Trial - Register Programs:
Speedupmypc3 +
RegistryBooster2
Ad-aware2007 +
Free apps:
Spybot search and destroy
Adaware personal se
I've got the above top 3 and have no problems. all i get once a week is cookies and few trackers. Which are cleaned and removed each time i scan. PC runs perfectly.
Use these along with what is said in the first post. I.e your anti virus software and also your defrag etc your computer should be fine!