Laptop Overheats On 64-bit, But Ok On 32-bit

a while back i switched from 64-bit to 32-bit due to one thing: over-heating!

when i had 64-bit, my laptop overheated and kept on shutting its self down, even after watching a 10-minute Internet video.

i searched everywhere to figure out wtf is wrong with my laptop. first i thought i had faulty hardware, installed windows 7 32-bit on another volume and it never overheated, not even after playing gta iv for 3 hours (dident even get hot) but in 64-bit it takes less than 5 minutes for gta iv to over-heat my computer, wtf is up with that?

then i thought it was drivers - went on amds site and downloaded every driver: graphics card, cpu exc.

no luck!

so i finally switched to 32-bit..but see, gta iv runs even worse.

64-bit: 30-35 fps

32-bit: around 20-25fps

my specs:

amd athlon 64 x2 dual-core processor @ 2.0ghz

ati radeon 3100 hd 256mb dedicated/ 1.2gb shared

3gb sdram @ 800mhz (but in bios i took off 1gb shared ram so then i had 4gb of ram on windows 7 as 526mb is enough!!!)

320gb hard drive

also, i bought a cooling pad thinking that would help. still overheated, but got an extra few minutes watching Internet.