[Markh]

Xplorer2 Lite (tons better than Windows Explorer)
IrfanView (small and quick picture viewer/converter/resizer with batch processing ability)
CutePDF (free PDF printer)
Process Explorer (see what's running)
Synctoy (great for syncing tools/apps on your USB drive with a folder on your HDD)
Cobian Backup (good freeware backup software)
Everest (formerly Aida32, great system information program - good for IDing the RAM or M/board or whatever without having to open the case)
VMware Player (you can create a VMware machine with VMware Workstation and then install the free VMware Player on the custmers PC to run that machine)