I've had some issues with cpu heat causing slowdowns. I solved it by removing the heatsink, cleaning up the fans and applying fresh thermal compound. I use Arctic Silver 5, I think it works much better than the standard heat pads the system ships with. They can dry out and crack over time. It brought the temps down quite a bit for me with my m9700.
My cpu goes from 49 deg C up to the low 80's under heavy load. The gpu temps you posted are normal, so the gpu(s) may not need thermal grease, but if you're going to be in there anyway, I'd consider applying AS5 to both gpu's, the cpu, and the SLI chip. It's all in the tutorial, and it's much easier than you'd think. Just be careful of the pads on the memory on the gpu's, as you'll need to reuse them, or source some new ones.
If you don't think it's temperature, make sure you've got all the latest drivers from Alienware, especially the chipset drivers. I assume you installed the hd controller drivers (RAID drivers) during your install, or you wouldn't be seeing any hd's...
I have read about people that have had to install Vista after an install became corrupted, so you might consider doing the install all over again to make sure it's not vista related.
My bet is a good cleaning and replacement of the thermal compound will probably take care of your issues.Here is an excellent tutorial on applying AS5 to the cpu and gpu's, with pictures.