While you're at it, tell me, are you using the default HP
PSU?
And if you are, do you know what the power rating is?
Nvidia GPUs, particularly monsters like that are power hungry and will cause brown outs, shifting into low power mode when it happens.
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Notebook: Apple Macbook Pro 13" i7 2.7Ghz (3.4Ghz max) 8GB DDR3 1333Mhz (Mac OSX 10.6.7)
Desktop: ASUS Rampage Formula X48
Intel Core 2 Quad Q9450 (Yorkfield) @ 3.60Ghz (Folding SMP Linux)
Running Fedora 15 Linux (GNOME 3)
Dual Dell 2407WFP 
Drivers, Games, Demos, Mods and Overclocking Tools At AOAFiles