Dell Studio 1558 - Windows booting and video display problem - video drivers?

Most of the time now, this machine won't boot. I ran the pre-boot hardware diagnostics TWICE, and it passed all of the different tests. No video problems, no hard drive or memory errors, nothing.

There seems to be some kind of video driver problem, at least that's what the sometimes-appearing BSOD suggests. I ran a Windows repair a few times, which seemed to temporarily fix the problem completely - but the failure to boot returned after the machine was turned off and rebooted a few hours later.

Sometimes, when the no-boot occurs, I can hook up an external monitor (no display on the laptop at all - black screen)  and re-boot into Safe Mode. This laptop is running the Mobility Radeon  HD5470, and the screen responds perfectly when running the pre-boot hardware tests. I suspect a video driver problem, but Dell shows no upgrades to the version that shipped with the machine.

This laptop was purchased directly from Dell, and came without any Repair or Restore disks. 

I am thinking of somehow re-installing Windows, but I would lose the copy of MS Office 2010, and of course, no restore disks for that, either. I could retrieve the Office key, but there is no restore media with which to use it.

I read on these forums that there is a Windows Repair DVD that exists for this machine. Does anyone know how to get one from Dell?

TIA!