If, for some strange reason since it
never happens

, you've used a crack to install CS2, the crack might be corrupted, try another.
Other possible issues could be;
-Not enough RAM
-Corrupted Install (doesn't make sense, since you re-installed.. but, something could be corrupting the install each time you try to install it, like another program, or a virus)
-Photoshop is resource intensive, how up to date is your cpu? I found myself waiting up to a minute for it to load on my old Celeron D. How long are you waiting for it to load before rebooting?
Good luck