It would sound like any other missing hal.dll incident but I assure you it is not...
I recently bought a Dell Inspiron 9400 (Intel C2D T7400, 2GB DDR2-667) and it came with Vista Home even though I had requested XP pro. Luckily I had Xp pro, so I installed xp pro and during reboot it came up with Windows cannot start blah blah blah missing or corrupted file - hal.dll
Okay, I've been through this before. So I put in the OS disk and it won't even start up keeps going to the same file is missing message.
I've even tried using the dell restore cd, vista os cd but I can't get past that missing file screen. Can't get into safe mode or anything... nothing just that missing file black screen.
I tried booting from usb drive and that didn't work either and I can't jump from floppy because it doesn't have one!