Was working, now hangs at boot

Hi all,
I have the 64-bit RC dual booting on my PC along with XP Pro SP3.
Win7 has worked great for a few weeks now, but today a big issue cropped up.
I was working on a CAD file (I'm a Civil Designer), when my PC spontaneously rebooted, as though I have pressed the reset key. There was no error and no visible BSOD.
After reboot, the machine POSTs fine, then presents the OS selection menu.
I choose "Windows 7". The screen goes to the black screen with "Starting Windows" on it, and hangs indefinitely.
The animated windows logo nevers appears, not even the little glowing dots at the beginning of the animation.
I am unable to boot into any version of safe mode, nor can I launch the "repair windows" option after an unsuccessful boot.
Perhaps most oddly, I can't even boot from the DVD to attempt a repair install!
In all cases, the system hangs at some form of loading screen. For safe mode, it locks after loading "...\system32\DRIVERS\CLASSPNP.sys" The screen says "Please Wait..." at the bottom and sits there until I reboot.
If I try to boot from the DVD, it shows the "setup is loading files" message with the progress bar, which seems to complete.
It then goes to the same "Starting Windows" screen and hangs.
I have tried removing some of the RAM, with no effect. I have run memtest86 from a boot disc for over an hour, with no errors.
I can boot into my XP install with no problems, which is where I am typing this from.

Does anyone have a clue what could be causing this?!
Windows 7 has impressed me so much that I've taken to using it as my primary OS, so this XP install is behind on updates and all my work files are on the win7 drive.

Any help greatly appreciated,
Elmojo

Basic system specs (from Belarc Advisor) below, detailed specs available if needed:
Operating System: Windows XP Professional Service Pack 3 (build 2600) & Windows 7 RC 64-bit of course!
Mobo:EVGA 132-CK-NF78 2 (nForce 780i)
BIOS: Phoenix Technologies, LTD P08 09/09/2008
Processor: 2.80 gigahertz Intel Core2 Quad Q9450 @2.80Ghz (very slight OC)
Memory Modules: 6GB Corsair DHX Dominator DDR2-1066 (2x1GB and 2x2GB)
Optical: (2) PIONEER SATA DVD-RW DVR-215D SCSI CdRom Device [CD-ROM drive]
HDD: (1) WD Velociraptor 300 SATA2 10k rpm, (1) Seagate 1TB (ST31000340AS, 1000.20 GB, rev SD15, Status: Healthy)
GPU: (1) eVGA GeForce 8800GTS 512MB (G92)

You have an unsigned/incompatible driver/hardware issue that 7 wont let go any further. Usually creative give the biggest grief there. If you have a creative card pull it from the MoBo and see if it boots.

Aha!
I do have an X-fi card!
I'll try pulling it and report back.
Thanks!
Elmojo

How can this be done on a laptop?? im currently installing RC1 on my "old" toshiba (it runs Vista fine havent tried win7 yet but are trying to install RC1)

If it runs Vista fine then in most cases it should run 7 fine, u first install it and then see whether u have any errors or so...

It hangs on CLASSPNP.sys on startup.
I havnet finished installing yet cous it hangs

The laptop is a Tecra T4 (T40E) by the way

Will it help to unplug LAN? since its a laptop it will be hard to unplug the WiFi card