sounds like harddrive failure, or bios cannot detect the harddrive for whatever reason

bios itself is a program run by the motherboard, which controls the rest of the computer's hardware. The next thing to be booted after bios is the harddrive, which stores the operating system.

If it stalls at this point, chances are there is either a configuration problem with your harddrive, or it's shot. Check to see if bios detects your harddrive, and if it does, you have bigger problems than a non-detected harddrive.

Dell is decent about warranty, especially on more expensive laptops. This early on if it's exhibiting ANY problems you should make full use of the warranty. There's no point in trying to mickey-mouse a laptop that's still under a good warranty.

This may be of no use but when you push F12 did you check to see that the HDD drive is the first in the list?

As a dell certified technician this is one of three things. Either your operating system somehow became corrupted. The hard drive failed. Or the Ram is bad. First thing to do would be to run the dell diagnostics. Boot your computer up holding down the Fn key. This will load the dell PSA diagnostics and run a quick test on hard drive memory and processor. If in the first 2 minutes everything passes great. Your hard drive is most likely fine. Next you can continue running the memory tests or you can focus on the operating system. Boot to the operating system install disk and then run the windows vista startup repair. It is an automated process that can resolve most issues. You may also want to enter the WinRE and run chkdsk /r to check the hard drive for consistency. If something is failed call Dell and get it replaced