You're probably running an old DOS program that attempts to directly access
the hard drive through BIOS commands, which is a no-no under XP (or any
modern Microsoft OS). Instead, programs are expected (indeed REQUIRED) to
use Windows functions in order to ensure security and prevent damage to
those devices (which could affect other processes). Older DOS programs use
to directly access the hardware all the time, when it was the only option
available, but those days are long over. What does all this mean to YOU?
Forget about using that particular program any longer under XP, it's
history, time to find a Windows compatible version that performs those
functions.
Btw, the version of DOS that you see in XP isn't DOS at all, it's an
emulator. It's the DOS emulator that trapped the program's attempt to
access the hardware! Had it actually been a REAL DOS environment, like that
found under Win95/Win98, or of course, MS-DOS, it would NOT have generated
such an error. Of course, these OS's are more "fragile" precisely because
rouge programs can muck with the hardware.
HTH
Jim