My solution was to buy and install a program that removed trojans/virii and protected my computer against invading virii on a realtime basis. The program I use (ESET NOD 32) runs in the background regularly, does not use much overhead or require much vigilance and is not expensive. I' been problem-free since I installed it.
I also use a FREE program that cleans the registry and removes unwanted cookies, etc., called Advanced System Care Ver. 3. Feel free to research by googling those keywords and zee if they would work for you. My system guru recommended them and were no problem to use or install.
Here's a note from their (ESET NOD 32) documentation on Prevention:
When you work with your computer, and especially when you browse the Internet, please keep in my mind that no antivirus system in the world can completely eliminate the risk caused by infiltrations and attacks. To provide maximum protection and convenience, it is essential to use the antivirus system correctly and adhere to several useful rules.
According to the statistics from ThreatSense.Net, thousands of new, unique infiltrations are created each day in order to bypass existing security measures and bring profit to their authors"all at the expense of other users. The specialists at ESET’s virus lab analyze those threats on a daily basis and prepare and release updates in order to continually improve the level of protection for users of the antivirus program. An incorrectly configured update decreases the effectiveness of the program. For more information on how to configure updates, click here.
Download security patches
The authors of malicious software prefer exploiting various system vulnerabilities in order to increase the effectiveness of spreading malicious code. That’s why software companies watch closely for new vulnerabilities in their applications to appear and release security updates eliminating potential threats on a regular basis. It's important to download these security updates as they are released. Examples of such applications include the windows operating system or widely-used internet browser Internet Explorer.
Backup important data
Malware writers usually do not care about users’ needs, and the activity of malicious programs often leads to total malfunction of the operating system and the deliberate damage of important data. It is important to regularly backup your important and sensitive data to an external source such as a DVD or external hard drive. Precautions such as these make it far easier and faster to recover your data in the event of system failure.
Regularly scan your computer for viruses
A regular automatic scan of your computer with the proper settings can remove infiltrations that may have been missed due to your computer containing old virus signature updates.
Follow basic security rules
This is the most useful and most effective rule of all " always be cautious. Today, many infiltrations require user intervention in order to be executed and distributed. If you are cautious when opening new files, you will save considerable time and effort that would otherwise be spent cleaning infiltrations your computer. Some useful rules are:
do not visit suspicious websites with multiple pop-ups and flashing advertisements.
be careful when installing freeware programs, codec packs, etc. Only use safe programs and only visit safe Internet websites
be cautious when opening email attachments, particularly those from mass-mailed messages and messages from unknown senders.
don't use an Administrator account for everyday work with your computer.