Power down your computer. Hold F12 at the Dell BIOs screen and run the diagnostics, check that all passes. If it does then attempt booting up with your WIndows Vista DVD and running a starup repair.
I have a dell inspiron 531s vista  every time i restarted my computer it would give me an error message and told me to push "F1" to retry, well  i resently bought a dell oprtplex 8200 that the hard drive was still in it, i tried to put the 120 gb hard drive in my inspiron (while it was on) and it didn't show up so i restarted my computer and it wouldn't load windows i tried safe mode and all that but i cant figure out what hapened to it. i was wondering if i might need to buy a new motherboard?
windows has failed to start 