This item is from the Yet Another Enhanced IDE/Fast-ATA/ATA-2 FAQ, by John Wehman and Peter den Haan with numerous contributions by others. (v1.92).
If you've used Win95's fdisk utility to partition your drive, you may run across a nasty bug.
Win95 supports extended int13 calls to break the 8GB barrier. To avoid problems with old versions of DOS, partitions extending beyond 8GB must be made invisible. Unfortunately, the Win95 FDISK sometimes hides partitions this way even if your drive is much smaller than 8GB. Incidentally, this also hides them from all other operating systems, including old versions of DOS, and can cause all kinds of problems.
Under circumstances, these new partition types can completely mess up things when going from the Win95 graphical shell to MS-DOS mode. Drive contents may appear to be corrupted or be replaced by the contents of C:. Don't try anything fancy when this happens; it is really easy to corrupt your data. Don't use the "Restart in MS-DOS mode" option and don't run programs configured to run in MS-DOS mode. MS-DOS windows are still fine.
The most comfortable way to fix this is to change the partition types using Partition Magic <http://www.powerquest.com>, but ONLY version 2.03 or later. You can get an update patch for older versions.
The alternative is to back up your data and repartition using FDISK /X, which disables the use of the new partition types, or DOS 6 FDISK. Also be sure to apply the Win95 ios bugfix and other fixes available from Microsoft's web site.