What kind of files did you delete? Did you delete any programs? What player are you using? What OS are you using?

If you're only getting sound with videos, you probably need codecs. Have a look at the thread below, there's info about codec packs & alternative players. The XP & K-Lite codec packs are popular. There's a link to a Vista codec pack as well. Or you could try VLC player...it's free, has codecs installed & plays most things.
CODECs list for Movies/Audio/Alternate players / Video help forums/ video-mp3 fixers