You won't find a popular virus scanner that is zipped up. If you want a quick way to scan your PC for viruses (although you still need to get a virus scanner), try the
Trend Micro Housecall online scanner.
Another solution if you want a virus scanner quickly - try going down to your local newsagents and look at the PC mags there. One of them is bound to have a virus scanner on the cover disk.
The free virus scanners are only around 10-15MB in size. On today's broadband connections it won't take more than a few minutes. Worth the wait for the protection you will get.
EDIT: Doh! Ben beat me to it
