I've been meaning to post this information, but just haven't gotten around to it until now (slack I know). Anyway my point to this post is, don't run CA Anti-virus (formally Vet for some users) if you're running any version of Windows Vista (including SP1).
I've personally run into problems on both AMD and Intel based computers where the explorer process will start using 100% of the available CPU power (on the active core), which can last a few minutes at a time. I found this was caused by the CA Anti-virus real-time scanner and the only way to get around the problem is to disable it. BUT if you do disable the real-time scanner then you have to remember to manually scan every download and email attachment otherwise you could get infected (because nothing is being scanned automatically any more). Some good news is that CA Anti-virus still works perfectly fine if you are running 2000 or XP.
As an alternative to CA Anti-virus I'm now testing Avast! and I'm impressed (apart from the voice alerts). Some other anti-virus packages that I haven't yet tested on Windows Vista but I would still recommend are NOD32 and Kaspersky.