my workhorse computer is running fine on a fully patched W2k. So I doubt, your problem is related to some MS patch.
You are aware that some music CDs and Video DVDs install “copright enforcement drivers” (these are basically virus-like, you may google for “sony rootkit”)?
Maybe something like this happened on your system?
That would be my guess as well, if both systems had played the same disc or if the are networked with shared drives, etc.