Graphics "stutter" while gaming, video card, HD or CPU problem?

Here are my specs:

P4 3,06Ghz

512 MB RAM

60 GB HD

GeForce fx5200Go

bios a26 (just noticed I can upgrade that one ;)

Ok, I've had this problem for quite some time, got newest videodrivers from dell's own site, I've defragmented when necessary

I never did expect a laptop to be able to run with high-end performance on never games, but I would expect it to run smooth on 1024 x 768 with low graphic settings?

Problem goes like this (in this example, NFS Underground, easy to notice on racing games)

Pretty much all graphic settings are on "low", 1024 x 768, I start gaming and everything runs smooth. Then for maybe 0.3 seconds, everything stops, then I jump back into the game again. Happens with a lot of other games too, and I *know* the computer can do better, it can't be all related to poor graphics engine in the games?

Star Wars: KotOR ran good enough, then suddenly same problem starts to appear here as well. And that's running in 800 x 600!

Some first person shooter games work well, some other just stop for a blink of a second to then just run smooth again. Temperature of CPU sometimes been 71-72 degrees, would this be a limiting factor? Or is the harddrive (4200 rpm) too slow to load enough data?

Max Payne 2 worked excellent, no stutter/graphics problems, at least nothing that I need to mention.

I use it probably 80 % for gaming, and this is getting quite annoying... I'm way over the 30 day period, so that won't help me.

I will eventually buy a desktop anyway, but I need a temporary solution. Would an external harddrive maybe speed things up? Any other 3rd party programs that may help?

I have recently reinstalled Windows XP Pro, and I can't remember missing any drivers. Are there any "classic" mistakes while reinstaling that could cause this? (I pretty much had the same errors prior to reinstalling/reformatting).

Hope someone has run into a solution on this problem, tech support didn't seem to understand my problem at all.

Thanks in advance.