I know what you mean, I am now having to virus check my PC every day. I'm new so still learning the rules (think I've learnt now ie the only 1 download from a user at a time rule DIDN'T REALISE still I started reading).
On a daily basis I'm picking up about 9 - 14 viruses a day, you should have seen my partners face when he cleaned it up for me one day (hadn't checked for a while) and he found 97 viruses. Oh boy!
Is there a way you can check before you ask to download the file, I'm already not dowloading zip files (learnt my lesson) and guessing the MBs of what a file should be but still picking up viruses. Generally downloading avi, mpegs and the other m... Also when people are uploading from me are they able to hit me with viruses?