ntdlr missing could have one a few causes. See info at How To Fix NTLDR is Missing and Related NTLDR Errors. The most common causes and fixes are there.
Again, where did you get the Windows 7 install software from?
Did you check to see if the computer Windows 7 compatible? Download Windows 7 Upgrade Advisor from Official Microsoft Download Center
Download and run the Windows 7 Upgrade Advisor to see if your PC is ready for Windows 7. It scans your hardware, devices, and installed programs for known compatibility issues, gives you guidance on how to resolve potential issues found, and recommends what to do before you upgrade.