OSX 10.6.8 - Admin Account settings - Can I revert or reset to default?

Mac Pro 1,1

Dual Core Xeon

2.66 GHZ

I recently upgraded to OSX 10.6.8 and can't get iTunes to launch under my primary Admin Account: itunes 11.0.3 won't launch in 10.6.8

We seem to have narrowed the problem down to account settings; iTunes will launch under an alternate account on the same computer.

So I can set up a new account to use on my system. But is there a way to zero-out, revert, or reset my EXISTING admin user account so as to take it to ground zero and see if I can isolate the problem from there?

Thanks!