Is it just an oversight that MPASM v3.50 doesn't list Windows XP in the MPLAB IDE 6.30 release notes? Farther down in the MPASM readme there's a blurb about Windows XP-J and Japanese characters? A bunch of the dev tools now support WinXP so I assume MPASM will work - just didn't see it in the list. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Operating System Support List for v3.50 ----------------------------------------------------------------- MPASM.EXE is the command-line version of MPASM Assembler. It is supported by the following platforms: Windows 3.1x Windows 95 Windows 98 Windows NT Windows ME Windows 2000 MPASMWIN.EXE is the 32-bit Window version of MPASM Assembler. It is supported by the following platforms: Windows 95 Windows 98 Windows NT Windows ME Windows 2000 -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics