You can open the case and not void the warranty if you are on the phone with alienware. I read that on their site somewhere, but I not 100%. I just got my 5750 yesterday and I wrote a review if you interested.
I just got my m5750 yesterday so i'll write my thoughts.
Specs (the important ones):
intel core duo 1.66Ghz
1GB ddr2 ram
17" widescreen 1440x900
80GB sata drive 5400RPM
ATI mobility radeon x1800 256MB
windows xp home
I ordered my 5750 last week. It just shipped today !!! I got the tracking number and everything, should be here Saturday, 8-26-06 This is my first alienware and I've been anxious to see it in action. I'll be sure to post a review also....