A number of antiviruses will ask you to delete their competitor's products

You can generally ignore this, just don't have one running when you are loading the other.

If one detects a virus, make sure that it is cleaned deleted, rather than quarantined, or your other AV will probably find it in the quarantine file

The important thing is to have only one running in interactive/real time mode .

Please remember if you have more than one, you will have to manually update the secondary ones regularly, or there is no point in having them.

I do not run PC-Cillin on XP, I use McAfee on that machine. I would have thought that you should have deleted the default guest account, on the grounds that it is a security risk in itself?

Whichever AV you choose, you should CAREFULLY look at the settings. Some will default to only scan "program files", this is pretty useless IMHO, you should scan everything.

Also make sure that any "heuristic" or behavioural scanning is enabled...this is your only chance of catching a new virus or variant. Basically, if it WILL do it....let it

Cheers