Windows Backup itself can generate a pretty decent image. I have used this several times with very good results. If you insist on paying, I would recommend Acronis TrueImage, it's really quite good, but Windows Backup has big advantages:
- Restore is available by booting your Windows installation DVD
- You can restore to any volume that you can get Windows Setup to recognize (load drivers when prompted)
Acronis on the other hand will:
- Perform encryption if so directed
- Compression can actually make things go faster if you're backing up to a 2.5" USB drive
Acronis can be a crapshoot though, if their linux-based recovery disc does not have the drivers for your hardware you're boned when it comes to bare-metal restore.
To use Windows Backup, just click Start, type "Backup", select "Backup and Restore Center", then click "Back up computer".