stand-by mode

Right-click on empty area of desktop and click Properties. Click Screen Saver and then click Power. There you'll find the Stand By tab where you can enable or disable.

thank you for your reply. I have made a little research about my problem and it looks that it is a little bit more complicated. I can use the stand-by option but after 3 seconds or so it returns to normal mode.
i used the help of windows and what i figured out is that when i ran the susfail.txt file it told me " Your computer could not Suspend or Hibernate,
because a device vetoed the Suspend or Hibernate request. "
i tried to disable relevant devices in the device manager but it didnt help
also - there was a program that i ran that told me that the problem was in the Bios but when i checked it looked fine.

if someone is up for the challenge i will be delighted. i spent almost 4 hours to figure it out and failed so far.

Look into your C:\ drive for a file called Nohiber.txt
If you didn't find it click Start/Run and type nohiber.txt and click OK

Find it and open it in notepad.
It will tell you which driver is causing the hibernation or stand by problem.

stand-by mode
thank you for you reply -

it says - " PCI: Bad IRQ Holder "

what should I do next ?

IRQ are like lines which are used by hardwares to get the attention of the CPU.
Your problem seems to be with hardware installed within the PCI slots like Video card, Sound Card or Network adapter.
Try to re-install these hardwares with the most updated drivers from the manufacturer site.