Run ESET Smart Security V4 AntiVirus+AntiSpyware+Firewall (really light, doesnt slow down PC and never had a virus get through it)
Disk Defrag once every few days.
Ccleaner every day (Right click recycle bin-->Run Ccleaner)
Uninstall ALL Programs in Revo unistaller in advanced mode instead of normal windows uninstaller (VERY Helpful)
Do a weekly scan for malware with Malwarebytes Anti-malware (been doing this for a year, never detected anything) ESET handles everything.
Do disk cleanup every month.
Enable System restore.
Keep Games on E:\ Partition, music and pictures on D:\, Programs (portable programs

) On H:\. This way if I haft to re-install for any reason I have all my pictures, music, most programs and all my games =)
Yea, Windows 7 runs as fast as the day I installed it. When I had NO programs installed, NO AntiVirus, No nothing.
Windows XP and Vista wouldn't do the same!
Windows 7 FTW!