i could find a romf or ya, i already have many n64 rom games that are playable on my comp through the emulator "Project 64".
Heres the site i use, it includes a MASSIVE amount of roms..
(priv message me for link)
heres the link for the english version(or should be) of the starcraft n64.
(Priv message me for link)
(Download acceleratior will not work, nor a few other downloaders, use Opera, IE 6, getright).
I'd think you could infact put the data from rom to pc. But it will be in .scm not .scx. And most likly 1.04 version or lower. Hopefully n64 n pc's version of starcraft share near the same engine so they read correctly....you know.....Maybe beta 57 format was used for n64 maps. I mean, n64 is crappy and beta 57 is crappy. Hell they go togeather! You can try ~_~, or you could just create the map from scratch, even though that would be very hard.
I have an extra question...
What was that N64 maps name, someone may have already converted it...