Please help. As i have problems i cant rezolve.

Problem 1
 Whenever i try to watch a video it will freeze at random. Will do the same 
thing regardless of the player im using( Winamp, Media Player) and even stuff 
online.

Problem 2
 Music files will start playing and then randomly distort. Its a kind of 
screeching sound that lasts a few seconds at a time at random points in the 
song.

Problem 3 is a combination of the two previous ones. Video start playing 
then freeze but the audio will continue to play but with the random 
screeching!

All the Video and Audio files are ones i have had on my PC for years and 
they have been played perfectly well many times in the past.

I am not %100 sure, but i think that this problem  started when i dowloaded 
a Windows recomended critical update which instaled Internet explorer 7 on my 
PC a few months back. Could be wrong but the timing seems to corespond.

Please help if you can.

Thank You.