My suggestions ~
Use Mozilla Firefox vs MS IE as a browser.
Grab the freeware downloads of AdAware and Spybot and run them weekly.
Grab the freeware version of AVG. It will run in the background 24/7 unless you disable it which is suggested when running AHII
Defrag at least once @ month.
And here's a biggie...if you get a screen warning saying some program you've never heard of has identified numerous infections, trojans, bugs etc. and is prompting you to run its program to remove the problems, STOP. It's likely to be a malware program. Malware is extremely difficult to cull out of your system once it's there...and you're the one who gets tricked into putting it THERE. Boot up the task manager (cntrl+alt+delete) and shut down your browser, making a note of the name of the program that popped up out of nowhere. Reboot your browser and Google the name. Follow the links and suggestions as to how to best proceed.