Computer hangs when playing games

Hi.

My desktop computer hangs when I play certain games, eg. Football
Manager 2005 and Settlers, for just a few minutes.
The games work fine on my laptop computer, so I thought it might have
something to do with the hardware/drivers.

I have updated the bios of my motherboard (Aopen AK-77 400 GN) and the
driver of my graphics card (ATI Radeon 9600 SE). The games have also
been patched.

I'm running on an AMD 2400+ with 512 mb RAM.

Does anyone have any tips for what I can look for/test?
Thanks.

--doNascimento