trouble reinstalling photoshop cs3

Recently, cs3 has stopped working for me. One day I tried to open it and it wouldn't respond. I tried uninstalling it and then reinstalling it and it didn't work - it says failed to install Adobe Photoshop CS3. All the shared components reinstall, but CS3 doesn't.

I downloaded the trial version of CS4 to see if that would work, but again it told me that Adobe Photoshop CS4 has failed to install. And again, all the shared components managed to install.

Can anybody tell me how to fix this?

try this
Matt Boto, "CS3 installs, but freezes when I attempt to load it (no splash screen... just loads forever)" #2, 18 Sep 2008 1:42 pm </webx?14/1>