it sounds like your desktop may be similar to mine. It formerly had a 6200 in it. The new 8600gt is fairly disgusting... with 512mb, PCIe, and a cooling fan so large, I had to disconnect one of the other PCI slots, and cannot use it any longer.
I would suggest either upgrading your desktop graphics card, or try using a fan on the laptop. perhaps even opening any compartments on your laptop that you can. If you look at pcConnection.com or similar places, you can find a really nice gfx card for like 125 bucks.
it makes a world of difference, at least it did for me, since formerly my gfx card was the worst part of my system.
You may also consider checking out the power supply. When I did some research of my own, and basically tearing my computer apart and putting it back together, I came to realize that HP sold me a desktop with a power supply that was inadequate for the number of components I have. So basically they sell you computers, with incorrect voltage and amperage going to the components, then they eventually fry out and intel, HP ect., keep taking your money.
just my .02
Shiggs