What other tools might I need?

Other suggestions have included a sector editor, and Norton Utilities components such as Disk Doctor (NDD). These are not suitable for use by the technically-challenged - any tool which can manipulate disks at a low-level is potentially dangerous. If you do use tools like this, make sure they're good quality and up-to-date. If you attack a 1Gb disk with a package that thinks 32Mb is the maximum for a partition and MFM disk controllers are leading edge, you're in for trouble.... A copy of PKZIP/PKUNZIP or similar compression/decompression utility may be useful both for retrieving data and for cleaning (some) stealth viruses. The MSD diagnostic tool supplied with recent versions of DOS and Windows is a useful addition. Heavy duty diagnostic packages like CheckIt! may be of use. There are some useful shareware/freeware diagnostic packages, too. Obviously, these are not all going to go on one bootdisk. When you prepare a toolkit like this, make sure *all* the disks are write-protected! Tech support types are likely to find that an assortment of bootable disks including various versions of DOS comes in useful on occasion. If you have one or two non-Microsoft DOS versions (DR-DOS/Novell DOS or PC-DOS), they can be a useful addition. DoubleSpaced or similar drives will need DOS 6.x; Stacked drives will need appropriate drivers loaded. My understanding of the copyright position is that Microsoft does not encourage you to *distribute* bootable disks (even if they contain only enough files to minimally boot the system) *unless* the target system is loaded with the same version of MS-DOS as the boot floppy. Support engineers will need to ensure that they are legally entitled to all DOS versions for which they have bootable disks.