the 7950's are better cards in XP than the 8700 cards...i would use the drivers off of alienwares website and you must install the driver on both cards or it wont work and make sure that they are for XP...
Also if you are reinstalling XP...
I just went on alienware this morning and noticed that the M17x and the M9750 are gone from there website...could this mean a new lineup coming sometime...
I would give it a week or so to let the grease works it way in to the cracks but if it doesnt start going down then i would reapply the grease and make sure the vents are cleaned with compressed air...I always apply grease to my gpu card...
if you are the original owner of the laptop and its still under warranty tell them to send you some thermal pads... or send you a new heat sink for you computer to cool it down... you must have gotten a bad rep....i had my m9750 start...