Im running windows xp with microsoft office 2003 all of a sudden i am unable to open .pps files in emails. Also i have core media player which successfully played an ogm file but when i tried to play it again it wouldnt open "core cannot render the file...file format not suppoted" yet it played the other day. My computer is running slow but no virus has been detected in nortons also i have run spy bot and ccleaner. Any ideas what could be the cause of these things suddenly not working. Thanks in advance.