I used it before but now use xp but I think you may find help here
http://www.microengineeringlabs.com/support/mplab.htm

Windows 95/98/ME

The search path is specified in a file called autoexec.bat, that should be located in the root directory of your C drive (C:\). You can edit the file with a text editor such as notepad, or run msconfig (Win98 only).

The path statement uses the format: PATH=path1;path2;.... Add the paths to MPLAB and PICBASIC PRO to the end of the line, separating each path with a semicolon.

An example path statement is: PATH=C:\WINDOWS;C:\PBP;C:\PROGRA~1\Microc~1\MPASMS ~1.
Notice that long directory names must be shortened to their 8 character DOS equivalent. For example, the "Program Files" directory must be shortened to "Progra~1".

Restart your computer after making changes to the autoexec.bat file.