I use adaware at work. If the spyware is to bad I'll just reimage the machine w/ ghost.
For antivirus my site uses symantec AV corprate. All updates, virus scanning, and removal can be done server side.
I have some programs loaded on all users profiles such as my spyware product like spybot or the antivirus like AVG.
If I wish to uninstall it , it seems that I ahve to go into each account and uninstall it as if i uninstall from just onne user it is stil present in the other users acount - so If I went into the Admin account would it uninstall it from all users ?? and therfore is it best to install products//programs like antivirus from the admin accont so that it is present in all users??