The same limitation also counts for Windows XP, so no, compiling under XP wouldn't solve the problem (Source;
MSDN)
If I were you, I would use a different tool than WED to build the levels. Or at least to bake lightmaps on your models. There is a vast amount of applications that can do the job without being memory hogs, and the results should also be way better than the WED lightmapper is able to produce.
You could try and ask Rondidon if he can give you some advice as I recall that he has great knowledge in this area.