I have seen this problem come up a few times. Some people think that having more than one antivirus programs is better than just running one. The problem is that some antivirus programs see other antivirus programs as a virus. This can cause one of the antivirus programs to try and remove the other one. The big problem with that is that antivirus programs like to bury themselves deep within the OS, and when another programs tries to remove it, it can cause major problems. Now if you think you might have a virus and you don't think your antivirus program is picking it up, then there are 2 more things I can recommend that you do.

1. Run an online antivirus scan. A good place to do that is at www.eset.com/onlinescan/. You can also check on Google as other companies offer free online antivirus scans as well, just be sure you are going to a recommended site as there are places that say they offer a free scan, but actually install malware on your system.

2. The other thing you can do is run the Windows Malicious Software Removal Tool. You can run this by going to your strat button, then click run, and type in the run box "mrt" without the quotes and hit enter. This will open the removal tool. You want to run the deep scan and hope it comes back clean. If not, Windows will give you the option to remove the Malicious Software.

After you have removed any Malicious software, and you are clean of any Virus, you should create a good backup and set a system restore point. One thing to remember is that if you got a Virus on your machine, and Windows created a system restore point, then the system restore point will still have the virus in it, even thoiugh you have cleaned your system. To remove the old systems restore points, you will have to disable and enable this feature. This will remove all old restore points and any virus that may have been in the restore points. Again, remember to create a new restore point afterwards and always backup your data before you do anything. One thing I can't stress enough is backing up your data.