How can i solve this weird probem??

We'll need to know more information, such as whether you are on dial up, what type of system it is (I mean Windows XP, Mac or whatever, not the brand name, like Dell), etc. Also, do you have issues like with this other appliances? It could even have something to do with how power is supplied to your home. Hmm.

I am using Windows 2000sp4
Pentium Celeron 733 mhz 195mb ram
My internet connection is ADSL
I dont think it has anything to do with the power supply because i just changed it. I started to have this problem when i upgraded from Windows98 which is weird because i dont face this problem before i upgraded

Hmm okay so it's not a wonky dialup connection.

This is beyond my scope, folks who would be better able to help you are off doing the Xmas thing. Should be more of 'em around, either later or tomorrow.

This sounds like an application is hogging the processor for a while and then letting it go so the PC is back to normal.
Usually it would be for only a few seconds though. Norton Internet Security tends to hog resources for a couple of seconds every so often.
There is one situation where I've seen this sort of thing happen for long periods such as the 20 mins you describe however.
I do not wish to alarm you but it is possible that your machine may have been hijacked and is being used as a zombie machine to send out huge amounts of spam.
You can easily check this though.
When the PC slows down have a look at the amount of data being transferred from the PC down your internet connection.
You can do this using Task Manager or just by keeping an eye on the light on the front of your modem.
If it stays on for the 20 mins and then when the PC speeds up it starts flickering as normal then there seems to be lots of data being sent from your PC during the slowdowns.
You could try disconnecting the computer from the modem when it slows down and see if it speeds up again or complains in any way.

I should also have said make sure you don't have any other programs running when you try this.
Don't play games or type letters or anything.
Just leave the PC alone and observe what happens.

I guess there is something hogging the processor for a while because the CPU usage in the task manager went to 100% when it froze. However, i dont know what application is causing that because of the freeze. Nothing registered in the processes list. When the freeze was over, it registered 98% on the system idle process. There is no data going down my internet. Is there another way to check??

OK.
What you need to do is open up Task Manager by right-clicking a blank place on the takbar and selecting Task Manager.
Then click the Processes tab in Task Manager.
Now across the top you'll see some titles like Image Name, User Name, CPU, Mem Usage and possibly some others.
Click on the grey CPU title box twice. Not a double-click.
This will sort the list by the amount of CPU usage that's happening.
So in normal conditions you should see something from the top down like :



This is the list from one of my machines and so it won't look exactly the same as yours. But the look is the same.
You'll see a whole load of things in that list that won't mean anything to you but don't worry about them.
And also some things on the list will move up and down as they need to take part of the CPU for themselves.
What you're after is finding out which process is eating up your CPU cycles.

All you have to do now is hang around and waif for the PC to 'freeze' and the CPU time to zap up to 100% and you will immmediately see at the top of that list which process is the problem.

Don't delete the process when you've found out what it is as it maybe something critical happening.
Just post the info and let's take it from there.

This is the image that i got when it froze


Heres a HJT log as well

Logfile of HijackThis v1.99.1
Scan saved at 22:24:12, on 1/5/2007
Platform: Windows 2000 SP4 (WinNT 5.00.2195)
MSIE: Internet Explorer v6.00 SP1 (6.00.2800.1106)

Running processes:
C:\WINNT\System32\smss.exe
C:\WINNT\system32\winlogon.exe
C:\WINNT\system32\services.exe
C:\WINNT\system32\lsass.exe
C:\Program Files\Sygate\SPF\smc.exe
C:\WINNT\system32\svchost.exe
C:\WINNT\system32\spoolsv.exe
C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
C:\Program Files\Alwil Software\Avast4\ashServ.exe
C:\WINNT\system32\svchost.exe
C:\WINNT\system32\regsvc.exe
C:\WINNT\System32\snmp.exe
C:\Program Files\Efficient Networks\Tango Manager\app\TangoService.exe
C:\WINNT\System32\WBEM\WinMgmt.exe
C:\WINNT\system32\svchost.exe
C:\WINNT\system32\svchost.exe
C:\WINNT\Explorer.EXE
C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe
C:\Program Files\Alwil Software\Avast4\ashWebSv.exe
C:\WINNT\system32\hkcmd.exe
C:\WINPENJR\win32\pphidpad.exe
C:\Program Files\Java\jre1.5.0_06\bin\jusched.exe
C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
C:\Program Files\iTunes\iTunesHelper.exe
C:\Program Files\Spybot - Search & Destroy\TeaTimer.exe
C:\PROGRA~1\EFFICI~1\TANGOM~1\app\TangoManager.exe
C:\Program Files\iPod\bin\iPodService.exe
C:\Program Files\MSN Messenger\msnmsgr.exe
C:\WINNT\system32\taskmgr.exe
C:\Program Files\Mozilla Firefox\firefox.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.yahoo.com/
O2 - BHO: AcroIEHlprObj Class - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Program Files\Adobe\Acrobat 5.0\Acrobat\ActiveX\AcroIEHelper.ocx
O2 - BHO: IeCatch5 Class - {2F364306-AA45-47B5-9F9D-39A8B94E7EF7} - C:\PROGRA~1\FLASHGET\jccatch.dll
O2 - BHO: (no name) - {53707962-6F74-2D53-2644-206D7942484F} - C:\PROGRA~1\SPYBOT~1\SDHelper.dll
O2 - BHO: SSVHelper Class - {761497BB-D6F0-462C-B6EB-D4DAF1D92D43} - C:\Program Files\Java\jre1.5.0_09\bin\ssv.dll
O2 - BHO: IeCatch2 Class - {A5366673-E8CA-11D3-9CD9-0090271D075B} - C:\PROGRA~1\FLASHGET\jccatch.dll
O3 - Toolbar: @msdxmLC.dll,-1@1033,&Radio - {8E718888-423F-11D2-876E-00A0C9082467} - C:\WINNT\system32\msdxm.ocx
O3 - Toolbar: FlashGet Bar - {E0E899AB-F487-11D5-8D29-0050BA6940E3} - C:\PROGRA~1\FLASHGET\fgiebar.dll
O4 - HKLM\..\Run: [Synchronization Manager] mobsync.exe /logon
O4 - HKLM\..\Run: [IgfxTray] C:\WINNT\system32\igfxtray.exe
O4 - HKLM\..\Run: [HotKeysCmds] C:\WINNT\system32\hkcmd.exe
O4 - HKLM\..\Run: [TangoManager] C:\PROGRA~1\EFFICI~1\TANGOM~1\app\TANGOM~1.EXE
O4 - HKLM\..\Run: [PPHIDPAD] C:\WINPENJR\win32\pphidpad.exe
O4 - HKLM\..\Run: [NeroCheck] C:\WINNT\system32\NeroCheck.exe
O4 - HKLM\..\Run: [SunJavaUpdateSched] C:\Program Files\Java\jre1.5.0_06\bin\jusched.exe
O4 - HKLM\..\Run: [QuickTime Task] "C:\Program Files\QuickTime\qttask.exe" -atboottime
O4 - HKLM\..\Run: [avast!] C:\PROGRA~1\ALWILS~1\Avast4\ashDisp.exe
O4 - HKLM\..\Run: [iTunesHelper] "C:\Program Files\iTunes\iTunesHelper.exe"
O4 - HKLM\..\Run: [SmcService] C:\PROGRA~1\Sygate\SPF\smc.exe -startgui
O4 - HKLM\..\Run: [Windows Defender] "C:\Program Files\Windows Defender\MSASCui.exe" -hide
O4 - HKCU\..\Run: [SpybotSD TeaTimer] C:\Program Files\Spybot - Search & Destroy\TeaTimer.exe
O8 - Extra context menu item: Download All by FlashGet - C:\Program Files\FlashGet\jc_all.htm
O8 - Extra context menu item: Download all links using BitComet - res://C:\Program Files\BitComet\BitComet.exe/AddAllLink.htm
O8 - Extra context menu item: Download all videos using BitComet - res://C:\Program Files\BitComet\BitComet.exe/AddVideo.htm
O8 - Extra context menu item: Download link using &BitComet - res://C:\Program Files\BitComet\BitComet.exe/AddLink.htm
O8 - Extra context menu item: Download using FlashGet - C:\Program Files\FlashGet\jc_link.htm
O8 - Extra context menu item: E&xport to Microsoft Excel - res://C:\PROGRA~1\MICROS~2\OFFICE11\EXCEL.EXE/3000
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.5.0_09\bin\ssv.dll
O9 - Extra 'Tools' menuitem: Sun Java Console - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Program Files\Java\jre1.5.0_09\bin\ssv.dll
O9 - Extra button: Research - {92780B25-18CC-41C8-B9BE-3C9C571A8263} - C:\PROGRA~1\MICROS~2\OFFICE11\REFIEBAR.DLL
O9 - Extra button: Share in Hello - {B13B4423-2647-4cfc-A4B3-C7D56CB83487} - C:\Program Files\Hello\PicasaCapture.dll
O9 - Extra 'Tools' menuitem: Share in H&ello - {B13B4423-2647-4cfc-A4B3-C7D56CB83487} - C:\Program Files\Hello\PicasaCapture.dll
O9 - Extra button: FlashGet - {D6E814A0-E0C5-11d4-8D29-0050BA6940E3} - C:\PROGRA~1\FLASHGET\flashget.exe
O9 - Extra 'Tools' menuitem: &FlashGet - {D6E814A0-E0C5-11d4-8D29-0050BA6940E3} - C:\PROGRA~1\FLASHGET\flashget.exe
O12 - Plugin for .spop: C:\Program Files\Internet Explorer\Plugins\NPDocBox.dll
O16 - DPF: {17492023-C23A-453E-A040-C7C580BBF700} (Windows Genuine Advantage Validation Tool) - http://go.microsoft.com/fwlink/?linkid=39204
O16 - DPF: {3E68E405-C6DE-49FF-83AE-41EE9F4C36CE} -
O16 - DPF: {6414512B-B978-451D-A0D8-FCFDF33E833C} (WUWebControl Class) - http://update.microsoft.com/windowsupdate/v6/V5Controls/en/x86/client/wuweb_site.cab?1149003068380
O16 - DPF: {6BEA1C48-1850-486C-8F58-C7354BA3165E} (Install Class) - http://updates.lifescapeinc.com/installers/pinstall/pinstall.cab
O16 - DPF: {DF780F87-FF2B-4DF8-92D0-73DB16A1543A} -
O17 - HKLM\System\CCS\Services\Tcpip\..\{4F54EF9E-4C57-47A4-8FDA-D1B97413349A}: NameServer = 202.188.0.133 202.188.1.5
O23 - Service: avast! iAVS4 Control Service (aswUpdSv) - Unknown owner - C:\Program Files\Alwil Software\Avast4\aswUpdSv.exe
O23 - Service: avast! Antivirus - Unknown owner - C:\Program Files\Alwil Software\Avast4\ashServ.exe
O23 - Service: avast! Mail Scanner - Unknown owner - C:\Program Files\Alwil Software\Avast4\ashMaiSv.exe" /service (file missing)
O23 - Service: avast! Web Scanner - Unknown owner - C:\Program Files\Alwil Software\Avast4\ashWebSv.exe" /service (file missing)
O23 - Service: Logical Disk Manager Administrative Service (dmadmin) - VERITAS Software Corp. - C:\WINNT\System32\dmadmin.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Program Files\Common Files\InstallShield\Driver\11\Intel 32\IDriverT.exe
O23 - Service: iPodService - Apple Computer, Inc. - C:\Program Files\iPod\bin\iPodService.exe
O23 - Service: Sygate Personal Firewall (SmcService) - Sygate Technologies, Inc. - C:\Program Files\Sygate\SPF\smc.exe
O23 - Service: Tango Service (TangoService) - Unknown owner - C:\Program Files\Efficient Networks\Tango Manager\app\TangoService.exe

I find it very strange..

http://support.microsoft.com/kb/328885

Well..I downloaded and installed the service pack(it is already sp4) but it didnt solve the problem ..My windows is up to date and all patches that is available has been installed..