Help needed researching computer virus statistics

I’m trying to find a website, or websites, that have computer virus infection statistics - number of PCs virus infected, PCs trojan infected, that sort of thing. I’d prefer to find a site that has these statistics on a monthly basis, but I’ll take what I can get.

(Oh, and I’d prefer not to have to pay for using the site, if that’s at all possible!)

Anyone have any ideas?

Bueller?

Thanks!

McAfee has a tool which might help.