I am probably a decade late with this question, but anyway.
I digged out a PDA with Windows Mobile 5, and installed SpaceTime Mathematics on it. It is a 30-day trial (and you can't purchase the full version anymore as the service is dead...). The problem is I installed it before I set the date and time on the PDA, and it thought it expired in 1999. I uninstalled it with the built-in uninstaller, and then reinstalled it (all that with WiFi turned off), but it didn't start over the trial period. I couldn't locate any remnant files, so I have to ask this desperate question:
Where should I search? or: How could I clean uninstall an app from WinMobile 5.0?