manual uninstalling

have to uninstall a program and install a newer version
the problem is that i cant just install the newer version of the program ontop of the other beceause it will get mess'd up and the 2 versions will both try to start their services

2th the program dont have a uninstall option as an exe file i can however uninstall it from add/remove programs from the control panel
though i want to make my install program handle this automatic but i'm not sure how many and which reg's i have to delete to remove the program

"Two wrongs doesn't make a right, but three lefts do..." :)

Why not try this way:
(1)Find a clean machine, run RegMonitor
(2)Install the old version
(3)After finished, from the RegMonitor's trace,
you can know the modified registry keys.
Then you can do it by your app now.