Windows crashes on startup, at desktop.

Ok, I'm running Vista home premium 64, and earlier today it froze (while on gmail, but i doubt that matters)
I gave it some time, tried ctrl-alt-del-ing, but to no avail, and had to crash it.
Since then, whenever I start it it gets to the desktop and as soon as I click anything it freezes up.
Safe mode works fine. I have tried going to mscongif and disabling startup items, it didn't work.
I cannot System Restore. It fails every time. If I try to System Restore from Startup Repair, i get "Catastrophic Failure 0x8000FFFF" if I just system restore from safe mode, it tells me upon reboot that it failed.
So yeah, I don't know what to do. I have a Dell guy coming in a few days to replace my motherboard (my headphone jack broke last week) and now this has happened..gaah!
Any help would be appreciated.

That failure has something to do with vista back up. Make sure that volume shadow copy service is enabled and running.
Right click on Computer in the start menu and choose Manage.

In the left pane, expand Services and Applications. Click on Services.

Scroll down to find "Volume Shadow Copy". It should have a status of Started and a startup type of Automatic. If not, you need to enable it:

Right click on the service "Volume Shadow Copy" and click Properties. Change statup type to Started and then click Apply. After clicking Apply, click Start. Now click OK and try backing up again.

And also please run chkdsk it may fix your problem

regards
acdcfan