How can a GPU be undervolted? also a question about the copper mod!

My friend has a Dell vostro laptop with an nVidia Geforce 8400GS GPU. His motherboard failed and was replaced recently by Dell. I've read that Rivaturner can be used to undervolt the GPU.
Can any one point me to a tutorial on how to do that? Also a toturial on how to use Rivaturner would help as I've never used it before?

Also, to help extend the life of his new motherboard/ GPU we thought about making the undervolt permanent. I mean we are planing if feasable to change the voltages with nibitor and reflash the GPU. I tried yesterday to do that but didn't go really far. I don't know how to retrieve the BIOS (i.e. .ROM or .BIN) file from Dell's BIOS update (i.e. .exe) file. Also I couldn't get nibitor to read the GPU file. I used nibitor 5.7.
Can the BIOS file be extracted from Dell's update file?
Can nibitor be used to read the GPU BIOS file? if it is YES, then how?

Last, the GPU temperature was maxing at 90c when playing NSF most wanted. I helped my friend to put two thin copper shims of 0.3mm each between his GPU and heatsink. We used AS5 as thermal past. The temperature dropped to about 82c. The laptop was not used for three weeks. Yesterday, when it was tested again (still with NFS most wanted) the temperature reached 84c - 85c. Is this normal?

 

Can You tell which exactly model it is? By who is bios made? When You saying that nibitor couldnt read vga bios is that mean that You have extracted or saved for example with gpuz actual vga bios?
Another thing better will be using only on copper shim like 0.6, 0.7mm. About different temp after 3 weeks I dont know if this normal but maby simple tempreture in the room was higher aswell then before thats why this 3c jump.

 

It takes time for the thermal paste to cure, probably a few days.

 

Updating the thermal paste will never get you more than a few degrees. 8C is really good. Thermal paste just makes heat move more betterer.

I'd suggest using a more consistent benchmark than playing a game yourself. The amount of heat will vary by complexity of the inputs and outputs, which, unless you're playing the same level the exact same way, you will not be able to simulate. Hence, benchmarks. I can keep my temps low in SC2 by loading a custom map and doing absolutely nothing, or I can spike them ridiculous high by spawning hundreds of units on a custom map. The user-component of this type of benchmark is inherently inconsistent and unreliable.

 

Try to use program Universal Extractor! I'm not sure but bios will be probably made by Phoenix if that You can read and follow this thread: http://forum.notebookreview.com/hp-...bios-oc-hp-8600gs-drivers-above-169-04-a.html.