OK, if you goto 'Run' and type regedit, this will give access to the registry.

you need to be very careful but basically if you use the 'find' option and search for adobe and/or photoshop in the software section and delete it that should be it.

best make a backup first though and do a system Restore point if using Win Xp.

i'd never advocate anybody deleting things from their registry unless they know what they are doing.........

Good luck.