I don't remember exactly but somehow, I managed to mess up with the Windows XP Registry and as a result MS Office along with MS Project 2003 and One Note start crashing. I un-installed all of these applications and re-installed them. All went fine but when I attempted to install Project Professional 2003, it gave this error:

"Project Professional 2003 cannot be installed when another instance of Project Professional 2003 is already present. To install this copy of Project Professional 2003, first remove the previous instance of Project Professional 2003 using Add/Remove Programs from the Control Panel."

I cann't remove it from Add/Remove Programs because it is already removed from there. I ran almost all well known Registry cleaning utilites including Norton WinDoctor, TuneUp Utilites 2004, Ashampoo WinOptimzer Platinum, Regvac, Regseeker, jv16 Power Tools but of no avail.

I manually searched the Registry for keywords like "Microsoft Project" and deleted the entries found with no success.
I searched the C: drive for any MS Project redundant entries and deleted them...still no success.
I searched Microsoft Knowledge Base for this error but could not find any matching results.

I am completely out of ideas. plz help.

yes

try this:

http://radified.com/video/damn_pc.htm

it won't help you uninstall project, but you'll feel a whole lot better. 

There's a valuable link. How did you ever find it?