zone alarm sucks. it has a mind of it's own and adds allowed sites even though you may delete them, close the program, reopen the program and there they are again. I didn't find the free version user friendly and their support for the free program is none.
free anti-virus programs work just fine, find one that you like, is easy to use and let it do it's thing (usually not a lot of choice they also have a mind of their own) Usually no support is provided for the free versions.
firewall a must, windows firewall seems to work fine as does the malware monthly download from MS.
spybot good and a good pop-up blocker helps. ie7 pop-up blocker is not perfect. I agree with fuzzy on this; never store your passwords on your computer, bad, bad, bad.
and then there is the obvious: NEVER CLICK ON AN E-MAIL ATTACHMENT THAT YOU'RE NOT EXPECTING, EVEN FROM A KNOWN SOURCE.