Dell dimension e520 stuck POST screen

Hello,
I've got a Dell dimension e520 that has been working fine for years and all of sudden it won't boot to windows. It basically gets stuck on the post screen after the dell splash.

I can get into the setup/bios and everything is as it should be, I started up via vista install CD and done system repairs and everything checks out ok. I've reseated ram and taken out the mobo battery and put back in again.

But still the machine gets stuck on the post screen and does't load into windows.

Any ideas anyone, I also don't get any beeping or lights on front of box either.