Spybot Search and Destroy for anti-spyware
AVG Free for anti-virus
Hijack This as a last resort if the above fail
CCleaner for cleaning up useless files like cookies, unused registry keys, temporary internet files, etc....
I would also recommend defragging your hard drive, possibly every 2 weeks but you can get by with once a month, maybe even longer.
My Computer: eMachines T5226 - Intel Pentium D Dual Core @ 3 GHz - Diamond Viper Radeon HD3870 OC Edition with 1 GB GDDR3 VRAM - 4 GB PQi Turbo DDR2-533 RAM - Corsair 650W PSU with 52A on single rail - TSSTcorp DVD-DL+-RW combo drive - Lite-on 52x CD-RW burner - Creative SoundBlaster X-Fi XtremeGamer - Logitech z5300e speakers - WinFast TV Tuner - Vista Ultimate 64-Bit. eBay name: Flightsimboy304