Windows 7 different freezing problems

[Brabus 999]

hi, about a month ago my vaio laptop started freezing on youtube . i mean everything was frozen and i had to restart it manually. and then it started freezing on avi files.wether i play the avi file on wmp, vlc or real player, the duration of the freezing was about a minute or two every 20-30 minutes on both the audio and the video. so far, this is what i ve done:

1-updated the video card . and everything else through vio update.
2- installed k lite codec 64
3- ran disc cleanup and registry cleaner through vaio care .
4- installed the latest realplayer version.
5- ran sfc scannow . i dont really know the results for the scan because i was away from the laptop the minute it finished.
6- scaned the computer with avg anti virus 2012 and no viruses were discovered.

results: the duration of the freezing decreased. now it freezes every 15 - 20 minutes for a second or 2 and the video fast forwards to keep up with the freezing and the sudio stops during freezing. and its really annoying because sometimes it freezes like 10 - 20 times a day. could it be from bitlord 2.0?

my system specs:
vaio laptop vpcea25fa
windows 7 home premuim service pack 1 and 64 bit
4 gb ram
2.27 gh cpu
ati mobility radeon hd 5145 graphic card.

plz reply to me as soon as u can ,any help is appreciated.
take care everyone.