Thanks Dodi - I'll try it when i'm home from work this evening. 2 questions:

1) Which files did you change the OS version in?
I tried changing the 4th byte in the following files (all 32 of them)
sw_rel.tbl and lng_rel.tbl
but it didn't work

2) Which image have you changed in this new file? the usw3_load file in all the LROC02O directorys?

Thanks again