Originally posted by patonb
...Was kickin down just fine till about 3 days ago...
How d'ya mean?
By underclocking do you mean AMD Cool 'N' Quiet technology?
If so, then this technology doesn't lower the CPU clock when the system overheats. All the technology does is lower the clock according to processer utilisation. So, if you're not using the laptop, or you're running a program which doesn't require 100% of the CPU's processing capacity, then the clock speed of the CPU will drop to save power and as a result of a lower clock speed, reduce heat dissipation.
Thermal throttling is what you're referring to. Lowering the CPU clock speed when the system overheats. I think this is a motherboard chipset & BIOS capability, not a feature of the AMD Athlon XP 64 processor.
Unfortunately, a hot system and low battery life is what you get when you put an non mobile processor (Athlon XP 64 3800+) in a laptop.
What temperature is it at? Go into your BIOS to find out, or download FanSpeed here http://www.almico.com/sfdownload.php
to find out. Post the temps here.