China DOS Union

I made a pqmagic image file for an EasyBoot boot menu. The resulting CD image file iso runs perfectly normally in Virtual PC, but after burning it to a CD and running it, this problem appears (system message: Not enough drive letters available invalid drive specification). I looked carefully at Autoexec.bat and config.sys but couldn't see any problem, so I have no choice but to ask the experts for help. The contents of the two files are as follows:
Autoexec.bat
@ECHO OFF
MSCDEX.EXE /D:mscd001 /L:Z
Z:\SOFT\PQMAGIC\MOUSE.COM
Z:\SOFT\PQMAGIC\PQMAGIC.EXE

config.sys
device=himem.sys /testmemff
device=oakcdrom.sys /D:mscd001
files=20
buffers=20
dos=high,umb
stacks=9,256
lastdrive=z

Not enough drive letters available invalid drive specification definitely means there aren't enough drive letters.
I suspect the “lastdrive=z” in config.sys is wrong. Please check carefully.

It's already defined as the last drive letter, so how can it still not be enough? That's exactly the part I don't understand.

Which command gives those error messages?

I guess it's caused by assigning the CD drive letter to Z. Try moving it forward a bit, for example MSCDEX /D:xxx /L:K, or just MSCDEX /D:xxx directly.

Or you can also increase the final drive letter specified by LASTDRIVE further, for example: LASTDRIVE=32 to specify the maximum number of drive letters as 32, instead of Z (Z means 26). Note: “LASTDRIVE=number” is an undocumented DOS usage, only for MS-DOS 7.x or DR-DOS. In that case, 6 more drives can be accessed, namely:


:
^:
_:
`:

Actually, this usage also works in Win2K, for example: SUBST ^: C:\TEMP, and then the ^ drive can be redirected to the C:\TEMP folder.

Really good, worthy of being the super moderator. Many thanks. I'll give it a try.

Learn how to ask a question first.
Change your post title to something better.
From now on, posts with titles like this may end up with only these three fates:
1。No one pays any attention. (This is the best-case scenario)
2。Moved to the off-topic section.
3。Deleted.