? Missing operating system?

Yeah, I was having fun playing Team Fortress 2, deciding I wanted to play some Just Cause 2 I set SLI to be on and restarted the computer, I left, came back roughly 15 minutes later, all was ok, hopped onto youtube, loaded up a video, set it to full screen 1080p. The computer then completely locked, nothing would do anything, but I could move the mouse. I restarted the computer to find after the part where it says "Starting Windows" and when the Alienware screen comes up it just locked right after the ding, the Alienware background was flashing black and then would come back again etc etc, the mouse had the little wheel on the top right, then the left, then the bottom it was strange. I restarted my computer to find the same issue. After several attempts of rebooting my computer, power draining etc, I decided to fire up my old computer to troubleshoot, I happened upon this thread: http://forum.notebookreview.com/alienware-m17x/507273-m17x-boot-problems.html
and I thought I had the same issue except for the hard drive failure and all that (Allthough that might be the case).

So I started up the computer, pushed F2, told the BIOS to reset to default settings and now the computer will only start up, show the Alienware red head thing with the options down the bottom (F2 for BIOS and F12 for boot menu.) The computer will then open up the normal console thing then only have a text in the top left saying "MISSING OPERATING SYSTEM."
Please help because I only got my Alienware 2 weeks ago .

Update: Hmm, I went into the BIOS menu and set the Hard Drives to be in RAID format, unfortunately they are now incompatable, stay tuned.

Update: Ok, I set my Hard drives to Raid 0, that fixed the operating system problem. The only problem now is that the computer is now doing the issue that I previously mentioned, it flashes upon startup and won't do anything, help please!

Update: I think I have the same problem that this guy had: http://forum.notebookreview.com/alienware-m17x/519726-m17x-r1-gtx-260m-driver-issues.html The only problem is that the thread is incomplete and with no answer . How can I disable SLI when I can't even log into my computer because of SLI?

Update: Started in Safe Mode, no problems. Started again in normal mode, same issue.

MAJOR UPDATE: I GOT AN ERROR MESSAGE, I finally have a lead: LoginUI.exe - Application Error
The instruction at 0x0207191a referenced memory at 0x00000000. The memory could not be read. Click OK to terminate the program. (When I click ok it just goes back to flashing and all that.)

 

Try installing windows 7 from the resource disk. I had to set my m17x hard drives to raid 0 three weeks ago and had to reinstalled windows 7. I hope this helps.

 

Thanks, but I am only going to use that as a last resort.

 

If it's only 2 weeks old, call dell, let them help you trouble shoot it. You're within your return period, so that can be your last resort.

I would try removing and reseating everything that's easy to get at, like the ram.