I take it you didn't back up this disk up, so you'll need to copy any data you want to save and reinstall Windows.
When you've gotten your system back like you want it, I urge you to get yourself an external hard drive and a good 3rd party backup program. You can set it up to do everything automagically at the time and frequency of your choice. 1 TB external hard drives are about $70 these days and a really good FREE backup program is the Easeus todo backup free which you can download from
http://www.todo-backup.com/products/home/free-backup-software.htm . That can save you a lot of time and frustration the next time something like this happens. Sooner or later it happens to all computers for one reason or another.
A sata HDD with Windows XP SP3 worked until the motherboard failed. An ASRock socket 939 was installed and on boot up got the "NTLDR is Missing" message. The computer will boot from another HDD and the HDD with the problem was scanned successfully with "CHKDSK" and several anti virus/malware programs. The repair option on the XP cd was used to replace NTLDR & NTDETECT.COM, fix BOOT.INI and fix the MBR. A new version of XP loads until it trys to start XP on the HDD and ends with the "NTLDR is Missing" message. Any thoughts on what to try next?