Did a backup of the computer with Acronis True Image and decided to try SD5 again using the latest build of the program. After uninstalling 4 I rebooted and installed 5. Worked okay as far as I could tell but for one thing. If I try to stop a scan in progress it locks up. The screen says:
Current Scanner: Finalizing
Scan Progress: 100%
Spyware doctor is completing the scan task...
Intelli-signatures: 0
Items processed: 0
The scan bar is full. It never comes out of this lock up without rebooting the computer. But since shutting down SD5 requires a reboot anyhoo that's a bit of a moot point.