What ya mean ya downloaded it? Is this some "Steam" sh#T or some kinda demo bro? I hear you when you said youve paid in full but
reason Im asking is if its online product you could have run into some copyright curse thats buggin your system right now.
I'd be looking for faulty 'Securom" or some other burn /copyright protect software that maybe has mis queued the proper manufacturers install path if thats the case
The tech forums here have some guros better then I who can help you get back up and running. Try a tour over here but member to spit all the details you can
Goodluck