No space in environment.
An error message like this can occur if you call SET_PP.BAT in AUTOEXEC.BAT.
To solve this problem, you must extend your environment memory. To do this, search a line
in CONFIG.SYS like
SHELL=C:\DOS\COMMAND.COM
and change it to the following:
SHELL=C:\DOS\COMMAND.COM /E:1024
You may just need to specify a higher value, if this parameter is already set.