My Computer is Ill

and I can't seem to fix it.
So I've come here to ask for help....
First the diagnosis
CPU-load is very irregular... mostly high though constantly between 50 and 100%
When I look at the processes the most active one is the Non active system-processes but from what I've read that can't be the problem.
The rest in there seems pretty normal.
The most annoying to me is that sound is slow. I can't play any Winamp file without it stuttering and the same goes for media player avi files and realplayer .rmvb files. And while internet is running just perfectly and without a noticable slowdown When I play a Youtube vid it also stutters.
Now The Computer has been opened yesterday and has been cleaned completely with use of pressurized air. Before that it was making more noise than usual and the smell wasn't really nice as well. both the smell and noise have dissapeared since then.
The single software addition was added by my sister a few days ago and is Sony Corporation Picture Packager VCD Maker. Not long after that the problems appeared. I've deleted the programs but it's still quite slow. Can't play any
So I've come here to ask for help....
First the diagnosis
CPU-load is very irregular... mostly high though constantly between 50 and 100%
When I look at the processes the most active one is the Non active system-processes but from what I've read that can't be the problem.
The rest in there seems pretty normal.
The most annoying to me is that sound is slow. I can't play any Winamp file without it stuttering and the same goes for media player avi files and realplayer .rmvb files. And while internet is running just perfectly and without a noticable slowdown When I play a Youtube vid it also stutters.
Now The Computer has been opened yesterday and has been cleaned completely with use of pressurized air. Before that it was making more noise than usual and the smell wasn't really nice as well. both the smell and noise have dissapeared since then.
The single software addition was added by my sister a few days ago and is Sony Corporation Picture Packager VCD Maker. Not long after that the problems appeared. I've deleted the programs but it's still quite slow. Can't play any