NTLDR is missing

Here's how it started. A friend had a major problem with her computer. I took her HDD out of her pc and connected it to mine to see if I could retrieve some important data for her. The HDD was a SATA 200 gig. My Master drive is also a SATA, so I connected it to a second SATA port on my m'board. Tried to start up my PC and immediately got the following: NTLDR is missing. Press Ctrl+Alt+Del to restart. After restarting, got the exact same message over and over even with the other persons HDD disconnected. What steps can I take to copy the NT loader back and what caused this? My HDD has 2 or 3 partitions. It boots from the first partition. Hope someone can help. Thanks

 

Go into bios and set that hard drive to boot first. ed

 

From Computer Hope:
New hard disk drive being added:
If you are attempting to add a new hard disk drive to the computer make sure that drive is a blank drive. Adding a new hard disk drive to a computer that already has Windows installed on it may cause the NTLDR error to occur.

Note that ADDING a drive which contains windows is NOT the same as installing windows more than once on one computer.

 

Set to boot from HDD but same problem still exists.
I'm running WinXP pro on a P4 3.2 GHz machine. HDD is 200gb SATA.

 

This is because your computer is confused by two hard drives on your system each containing a version of windows. The only way to solve it is to format or remove one of the drives.

 

Problem solved! Thanks. I had already disconnected the foreign HDD but the problem was that I still had my 2nd ide drive attached as always. I temporarily disconnected that, started PC and no problems. Have now reconnected my 2nd drive and all is well. Thanks again.