hd files problem
 

I'm not sure what's wrong w/ my laptop. I used to be able to play hd files without any hitch even though my laptop is kinda old already. Sometimes like right now, 'settings' (or something else) would be changed that all of a sudden I won't be able to play these hd (or high bitrate movie files) and I'm totally clueless of what's going on. Before, I would do clean install and I'd be able to play them again. But with my last clean reinstall it didn't do it. Can anyone help me with this one?

I've installed/reinstalled codecs that I used to have to run these cpu hungry HDs but it's still not getting it. Cleaned up the registry as well. I updated my drivers too to whatever's available online for which I didn't have to before and I'd still be able to play them, but now these things don't seem to work anymore. CPU performance would go up to 100% whenever it's playing a movie but at least it's able to play any movie without problems, but now the audio would play fine but the video would play like it's in slow motion (with bsplayer) or skipping frames (in wmplayer). Help pls. Thanks in advance.

Here's my laptop stats:
Intel Celeron CPU 2.80GHz
448 MB RAM
19 GB Hard Drive (free memory)
xp Service Pk 3