Help please...Framerate slows down and I don't know why

I barely know anything about computers but I do know that my computer can handle all the games I try. The games run good for a minute or two and then the framerate just slows right down and I can't play them at all. I recently just got this computer so not much is on it so i don't know what it could be.

oh im sorry im not sure how to check all that stuff but this is what I know}

256MB ram
Intel Pentium 4 1500mhz
Nvdia geforce2 MX
Im using Windows XP and im preferably trying to run runescape

sorry if this stuff doesnt help but im kind of clueless

yea the light is flashing quite a bit

well runescape ran fine on my old computer and it was about the same but maybe my hardrive is full? i've got like 1000 songs so if i were to compress them all would that help at all?

How recently? :? You didnt buy it new did you?

The gfx card should be fine for runescape, the graphics engine in that game is ancient. But RAM is an issue, get another 256mb or 512mb stick and that should help. Maybe you should overclock that P4.......

PS: That GF2 MX was the first 3D card I ever had, played most DX7/8 games ok. When it came to CNC generals, forget it. You knock over a tree, the game practically halts until it sinks into the ground and disappears. Then I got a GF4 ti4400....

Are you keeping them on the disk as WAV files?
If yes, get yourself an MP3 encoder (plenty of free ones on the Web, try tucows for example) and make them 160 Kbps mp3's. To play them use winamp or whatever software you prefer, again plenty of freeware for that. I don't think that's causing your problem with the game though.

Also try defragmenting the hard drive from time to time.