I've been running 11.04 successfully on an nvidia-based Thinkpad for over 5 months, thru multiple configurations and driver options, so you should be able to get things working with relative ease -- barring any weirdness with the Alienware HW I'm not familiar with.
But first I'd suggest you get yourself to what I call a KGC (Known Good Configuration), as your question leaves out all the background stuff I/we need to know to TS effectively.
Do a clean install of Natty 11.04. Accept all the defaults, except one. Wipe your current installation and reformat the drive. I'd suggest EXT4 as a filesystem. Reboot when complete.
Login to your clean install and first and foremost open terminal (or use the graphical update manager if you prefer) and type: "sudo apt-get update" (no quotes; let it do it's thing), then "sudo apt-get upgrade". When complete, reboot.
You should now be in one of two states: an accelerated driver has been installed (the unity panel is displayed on the left side of the screen); or, you're runnning in 2D mode (desktop looks like Maverick 10.10 with gnome panel on top of screen). If the former, you're golden; if the latter...
Do not simply click the driver update icon if it displays. This sometimes installs an older driver which may not be compatible with your newer system. Type and enter "additional drivers". When the dialog displays, choose either the Nvidia (version current) [Recommended] option, or the Experimental 3D support option (nouveau). I've had excellent success with the nouveau driver on my 460-based system. Reboot when complete.
If anything doesn't work as above, write back and detail what you did, and where things fell apart.