I have a reformatted hard drive in a Dell

re-formatting the drive erased the loader from the drive.. NTLDR is the boot loader that comes with all versions of windows.
You will now have to reinstall everything, including the raid driver if this is on a SATA drive.. Have you enabled USB keyboard support in the bios..? You may have to use a PS2 type keyboard to do this.. try re-installing the operating system from the original disk, if you dont have the disk, there may be a recovery partition hidden on the drive. If all else fails, either go to the compaq website and request a recovery disk be mailed out to you ( but dont hold out much hope as compaq dont like doing this), try and find the setup file on the hidden partition if it has one.. or, purchase your own copy of Windows and re-install it yourself. you may need to visit the compaq website to get all the drivers for the mainboard if they dont install with windows. go to www.computerhope.com/issues/ch000465.htm for a faily good explanation of what may be happening..