Was working fine, 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)

Hi Elmojo, welcome to the forums

That is a very strange problem, especially as you can't even boot from DVD back in to Windows 7. How long has the boot DVD hung on the "starting windows" screen, has it been for more than several minutes and is there any HDD activity during this time?

I know this is a bit late but..Acronis backups usually save you in these situations especially with new programs..if your xp is also 64 you should be able to copy files from the other hd or partition.. also you might be able to run your win7 install disk in repair mode from xp..or at very worst try an install as an upgrade to that partition..lot of mucking about and sometimes you get lucky.. but make an Acronis backups now of both xp and win7(as it is) to a seperate HD so at least you wont be worse off trying a few different ideas..good luck lets know how you get on..

Hi guys,
Thanks for the welcome!
@Ian: I have left it for several hours at the "Starting Windows" screen. There does not appear to be any HDD activity. If I am attempting to boot from the DVD, the disc spins down and does not get accessed again until I reboot.
@ronpeck: Thanks for the advice. I need to make acronis backups, but I haven't got around to installing acronis on this PC, since I had some issues with it on my last machine. The acronis background service was hogging resources like crazy, so I killed it.
I'll keep searching I guess.
Any other ideas pop up, please don't hesitate to share them!
Elmojo

Yep know what you mean about acronis..have you tried their rescue disk? allows you to backup and reinstall without having the program installed on that hard drive..also another little program I use in these cases is Partition Magic Floppy boot disks they boot up into a DOS like program and you are then able to create partitions; change partition sizes; format; rename; make partitiions Active; turn them off active state and make them visible only; or hide them..the last is handy when you fear contamination from another operation..Ihave found that these boot disks will work in other pc's if you can get hold of the PM boot disks you will be able to check the HD and partitions.. another thought is with Xp you can make a floppy boot disk in cases like this, dont know the procedure with win7 but someone out there might be able to help you. I am always mucking around and run 4 Hd,s on my main PC with 5th 1TB HD drive cady sys for safe away from machine backups..currently I have been playing around with win7 good except for some programs; win7 upgrade good all difficult to install programs work; win7-vista dual boot works well but there was trouble getting it into dual boot; vista with win7 in virtual pc (different Virtual programs)not a great success at this stage; I cant work out why your DVD install disk won't boot up..BIOS is set correctly?..check your dvd disk in another machine?, check your own dvd drive?..Check your hard drive with some program like P.Magic.. anyway luck stick with it

Im not having trouble with the Seagate DiscWizard that comes with a Seagate drive
I noticed you have a Seagate drive in your system so you could use the free software
Discwizard can also be downloaded if you didnt get a copy with the drive

I did however kill one of the two processes - The monitor service
One service is needed for discwizard to function (Schedul2.exe)
DiscWizard schedules the backup and restore using the schedul2.exe

Had some problems like that in the past myself, some of your files for windows 7 have been corrupted. the only way i could fix the problem on my pc Dual booted with Ubuntu and Windows was to format the whole drive and reinstall Both OS's........... I Personaly don't know why it won't run the repair, or even find the problem, When it happened to me it would hang as well, for hours.

Welcome to the site gimmick1668

Thanks for posting your fix

Quick update:
I decided to try the 32bit version of Win7, and darned if it didn't boot!
So now I have apparently narrowed it down to being a 64-bit issue.
Has anyone heard of certain chipsets or processors having issues running Win7 64-bit?
I know some processors (ie. P4) are not 64-bit compatible, but my Q9450 is, plus I had Win7 64-bit running perfectly for several weeks before this fiasco started.
Any ideas?

Have you tried re-downloading and burning the DVD again? It could be a dodgy DVD if it won't boot and gives you problems in Windows.