internal Application error

Trying to start Windows Media Pl;ayer 10, I get an error message saying An internal application error gas occured. The only piece of software I downloaded was a recommended registry cleaner which had a built in bachup. I decided that since this might be the problem, I hit the backup to rstore but it did not change the Media Player error message. I then went to GoBack but it would not run giving me a message that Symantec Integrator had a problem. I shut down and when I restarted I had only yje background on my desktop *no icons). I was able to get into DOS and get XPrunning with DOS commands. However I still am unable to start XP with a normal desktop without going intoDOS and GoBack and Media Player(which I removed and reinstalled) still won't run. Would appreciate any help.