Big NTLDR Missing Problem

Well, I have a doozy here that I can't understand. My friend's computer decided not to boot yesterday claiming to have a missing NTLDR. Looking this up, it would seem to be due to several things that can cause the boot record to be corrupted or loose cable etc. I tried all the easy stuff and none solved the problem. Then came the confusing part.

We put the harddrive in one of my computers and it is functional. In the native computer it is recognized in BIOS and will run all of Dell's diagnostics on the drive without fail. We unloaded all important stuff and were preparing to re install Windows XP but when it gets to the part to install it says there is no drive present. I have now tried a couple of other drives that are bootable and they will boot, but windows wont see them to install. Thus if i were to go get a new harddrive, we would have a similar problem. I have since used a ubuntu machine to reformat the drive in question and it still wont see the drive to install windows.

The system is a Dell Dimension 8400. I am told he has replaced some things in the system and I am unsure of the exact configuration.

Any ideas how to troubleshoot this and get me back to a working system?

The original Windows worked because it had the RAID drivers installed. When you formatted the drive, you lost your RAID drivers. Your BIOS has settings for RAID setups. Look closely, it has two different RAID controllers, the Dell and the Intel.
The SATA ports you are using go to the different controllers.

Maybe you can work with just one drive. There may be a setting for Not having a RAID present, otherwise known as JBOD (just a bunch of drives), which includes the possibility of just one drive.

You need the RAID driver to install Windows.

If you don't have your users manual for that computer, you can get it in pdf form, HERE.

(you can right-click my link and select "save link as" and download into computer for later reference).