error loading operating system


I hope someone can help.

I tried installing xp to a harddrive hooked up to my Vista machine via usb and got this error upon next boot. Booted to the Vista disc and followed all of the instructions in the neosmart wiki from beginning to the end to rebuild boot registry. Still have the error.

Checked my bios to make sure it was booting to the harddrive. I don't know what to do next.

All of the commands I ran from the command prompt were succesful. The only wierd thing was when I issued the command to rebuildbcd it said 0 windows installations found, but then it said it was successful. When I go to the repair menu on the Vista disc it does recognize the windows installation.
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Windows can't be booted from an external drive.
It's not designed to be portable, in fact it's designed not to be portable.
The EULA limits it to use on one PC. It expects to be inside that PC.
Sorry if this is not clear. The hard drive that I was loading the setup files for XP was for another computer being rebuilt. That hard drive is not part of the equation at this point, except for the fact using my Vista machine for this purpose was a mistake and now refuses to boot to the Vista OS. Can anyone help fix my failed boot registry?
Before running "startup repair" (3 times), disconnect all your other HDDs temporarily.
It often fails to locate the OS when other HDDs are involved, especially if there's a mix of SATA and IDE.
Thanks for your help. I tried your suggestion but didn't have any luck. The wierd thing was that the Windows installation was being recognized in the Windows Auto Repair, but not by bootrec. When I issued the /scanos command it said the number of windows installations was 0. I tried every command to try to rebuild the bcd registry but nothing was working. I did some more searching and found the solution which worked for me.

The fix I used was as follows:

Took the hard drive out and connected in another computer. Used Acronis True Image to make an image backup of the partition. Put the hard drive back in the original computer and ran the Windows Vista installation. After it copied the installation files and did the first reboot to finish the install, I took the hard drive back out and put it in the other computer again. I reimaged the partition from the backup. Put it back in the original machine and it boots perfectly in to my old installation with no data loss.