Found this information on Microsoft Tech Net:
Your first and most pressing question--what the hell is a RAW file system?--is easy enough to answer. It's simply a disk partition that has not been formatted with an NT file system, neither FAT nor NTFS.
As to the remainder of your problem, Mole feels that too much of the recipe is missing to cook up an entirely satisfactory answer. For instance, was the motherboard changed when going from the Pentium to the K6 processor? If so, there could very well be a problem with what Windows NT thinks is the disk controller and what is actually in the machine. This would cause problems in accessing the disk.
What's the fastest way to solve the problem? You may want to consider a complete re-install of the operating system, followed by a restore of data from the backup you performed prior to making the major hardware change. During the process of installing Windows NT, you will have the opportunity to format the drives to either FAT or NTFS.
One smart option for partitioning your hard disk is to create a smaller primary partition--say 2GB--using FAT, and to designate the rest of the hard drive NTFS. As you probably know, system boot files always reside on the primary partition. This way your boot up is fast, while the bulk of your files can enjoy the additional stability and security of NTFS. Note that with Windows NT 4.0, your hard drive may have only one or as many as four partitions. Going back to square one will let you customize your NT 4.0 installation for maximum performance.
Unfortunate News is that your data is probably unsalvagable. The only other possibility is that you could find out about this 'program' which can format your raw data to ntfs.