System lockup/reboots on boot up. Need help please

[Scream And Fly]

Hi everyone, I really need help from the community on this one...

I have a Dell XPS 720 which I've had since new. It has Vista 32-bit, fully updated. System specs are in signature. This machine uses the N-Force 4 chipset and is using the latest chipset drivers. The hard disk is always defragged.

This system has been absolutely rock solid since day one. Never a lockup. Never a blue screen. Until recently when it began giving me problems on boot-up.

Sometimes on boot-up it will get to the desktop, then the monitor goes black and I have to manually shut down the machine to reboot it. Other times it will boot to the desktop, then automatically reboot, giving me the error that Windows has recovered from an unexpected error. Other times it will boot normal. This can also happen if I reboot the machine anytime - it's not just on cold-boot. After a few tries, it will boot fine. I did a clean reinstall of Vista and the problem persists.

I should say, once the machine is booted, it's flawless. It never locks up and because of the booting issue I've gotten into the habit of just leaving it running, which is does just fine. I can game with it for hours and it runs absolutely perfectly. The machine has never locked up once it's successfully booted.

I've run Memtest (several passes) with no issues reported. I'm using the latest Nvidia drivers and this is essentially a pretty lightweight OS install. I don't have any USB peripherals connected except my keyboard and mouse.

I could really use some help on this one. I'm stumped.

 

[Dangman]

HDD scans?

 

[Scream And Fly]

HDD scans?

Yeah - checked for errors and of course virus/malware. I also did a clean install of Vista and it did not correct the problem

 

[Dangman]

Did you run a Memtest scan on each stick of RAM separately?
Reset CMOS?
Did you make sure there weren't any loose cables and such?

 

[Scream And Fly]

I did not test each stick separately - that's something I guess i need to do now. I appreciate it

 

[engiNURD]

It could also be a PSU issue. nForce4 is quite old.

pfft, just read the sig... there is no nForce4 for Core2! ugh, made me google it... grrrr.... despite those 1kw PSUs on the XPS 720's, I'd still suspect it because of its age (5+yrs old).

oh, and you could also double check all the connections inside if the system has moved at all.