CCleaner – System optimization tool – “Crap Cleaner”
PC Decrapifier – Automatically remove common trialware and annoyances installed by many big name computer OEMs.
Smart Defrag – free, fast hard disk defragmentation and optimization
UltimateBootCD – Many great tools on one bootable CD
Windows UltimateBootCD – you can boot to Windows from a CD – has a lot of great tools
TrueCrypt – free on-the-fly encryption. create a virtual encrypted disk.