if you originally had 98 or 95 on your box, this is usually the problem. it could also be the new HD (INT-13 ext, 0C system-ID)

Try sys C:
if it works, it'll be nice and easy.

here's another link: http://www.computerhope.com/issues/ch000465.htm
Cause:

1. Systems hard disk drive has FAT32 file system.
2. Computer hard disk drive has INT-13 extensions with a system-ID type of 0C in the partition table
3. The heads value in the FAT32 BIOS Pattern Block (BPB) is inaccurate.

Solutions:

To resolve the error message "NTLDR is Missing" follow the below steps:

1. Boot the computer with a Windows 95 or Windows 98 Startup diskette or another bootable diskette with sys.com on it.
2. At the A:\> prompt type:

sys c: <press enter>

3. After pressing enter you should receive the prompt "System Transferred". Once the file system has been transferred reboot the computer without the diskette and attempt to reproduce the error.