Performance Tools

Full Testing
PC Pitstop

Bandwidth
PC Pitstop
Bandwidth.com
BandwidthPlace.com

Online Virus & Security Checks
Symantec
Panda ActiveScan

Adware & Spyware
Spybot Search & Destroy
Lavasoft

DNS
DNS Stuff
Help: Wikipedia Encylopedia on DNS

Windows
CastleCops XP O23