Hi,
Realize you might have a drive gone or going bad - though it could be cabling or the drive controller.
You may need to try several of the commands here from your Windows Disk - Command Prompt
/FixMbr or /FixBoot or /RebuildBcd may have to use each in turn or more than once.
How to use the Bootrec.exe tool in the Windows Recovery Environment to troubleshoot and repair
startup issues in Windows Vista and Windows 7
http://support.microsoft.com/kb/927392
How to Boot to the System Recovery Options in Windows 7
http://www.sevenforums.com/tutorials/668-system-recovery-options.html
What are the system recovery options in Windows 7?
http://windows.microsoft.com/en-us/windows7/What-are-the-system-recovery-options-in-Windows-7
Repeatedly tap F8 as you boot :
How to Boot to the Advanced Boot Options in Windows 7 - select Repair Your Computer
http://www.sevenforums.com/tutorials/666-advanced-boot-options.html
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If needed
This is for XP however Vista and Windows 7 do not use this, give these a try anyway.
NTLDR is Missing Error Resolution
http://pcsupport.about.com/od/findbyerrormessage/a/ntldrmissingxp.htm
NTLDR is Missing.
http://www.computerhope.com/issues/ch000465.htm
How to fix: NTLDR is missing, press any key to restart
http://tinyempire.com/notes/ntldrismissing.htm
Hope this helps.
Rob Brown - MS MVP - Windows Desktop Experience : Bicycle - Mark Twain said it right.