I originally thought this was a hardware problem but I think I was mistaken... Anyway, I recently pieced together a machine from all working, new-ish equipment. Boots into BIOS just fine, recognizes the CDROM and HDD just fine and all the numbers look good. I ran a reformat and then a fresh XP install, everything seemed to go well but now the machine won't boot from the hard drive unless the OS install CD is in. Checked c: and everything seems to be accounted for. This is very frustrating. All advice is appreciated!

That makes absolutely no sense. What happens if you remove the CD? Did the installation actually finish? "So won’t you give this man his wings What a shame To have to beg you to see We’re not all the same What a shame" - Shinedown

I know, it absolutely doesn't. Yes, the install finished. Primary boot device is HDD, second CDROM. If I restart without the CD in the optical drive, I get a no OS on disk error message. If I have the CD inserted it loads a desktop.

How many hard drives are installed? Go to Disk Management after booting and see what it says there. You are looking for a basic disk. Is the hard drive SATA? If SATA is it connected to the first SATA port? Although SATA ports are all considered Masters a SATA controller usually serves TWO SATA ports. On some motherboards not all the ports are bootable.

Just the one hard drive installed, non-partitioned and as far as my not-so-extensive knowledge can tell, it's plugged in properly. Someone suggested it may have something to do with the jumper settings on the hard disk and dvd drive. It's an interesting idea but I have no idea how to correct it if that is, in fact, the problem.

This is a shot in the dark, but boot to the OS install CD. After it loads the drivers, press R to go to the recovery console. Login to Windows. When you get to the command prompt, type fixmbr and press enter. Some warnings will appear, but proceed anyway. After that, type fixboot and press enter. Again, you may need to accept any warnings that may appear. This may work, but it also may make Windows not boot at all. If you haven't installed programs or have any important files on the system, then this shouldn't be a problem. WinSimple Software

I was following the same path as rayburn. I suggest that in addition to what rayburn suggested to also type fixMBR in a separate operation when you are in the repair console. As far as where the drive is connected you should be using the port with the lowest number.