It rarely happens that MFT becomes corrupted. NTFS stores a copy of MFT that is called MFT mirror. If problem occurs, NTFS tries to synchronize these copies.
You can try to run Check Disk utility from Windows environment. Or if Windows is not bootable, boot from floppies or bootable CD-ROM to Recovery Console and run CHKDSK utility that could help you.
If the damage to MFT is serious, standard utilities might help you and you'll see "Drive cannot be accessed" message when trying to access the drive in Windows Explorer. In this case we recommend you to use third party software, like Active@ UNERASER for DOS or Active@ File Recovery for Windows to access and save your files to another drive, and then reformat the partition.