Oh, a sure way to check if you have the particular virus I had (W32.hybris.gen) is to start Dr. Watson. (start > run > type "drwatson") This will pop up an icon on the taskbar. Right click it, and pick the top item on the list. (I don't remember exactly what it says.) If you see a message that "<unknown> has modified Windows system files" you definately have the virus. I *think* McAfee has a new web based virus program available for free if you don't have a virus program. Since this type of virus is very new, you will need to update your definition files.
HURRY, this virus can download updates to itself, one of them can corrupt beyond repair ALL .exe files in the windows directory. I have several posts about some of the symptoms my computer developed. It began exactly with the message you just had!
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bloom25
THUNDERBIRDS