there are are some free virtualization-programs out there. win xp should be easy to find for nearly no money.
only downside is, you have to install nebula a second time in the virtual machine and get a serial for that. but then you can mess around with the programs, try patches in nat, ... and you won't destroy your working installation in mac osx.
system 1: windows 8 32 bit - samplitude prox/x3, tracktion6/7, reaper system 2: mac osx yosemite - reaper(32+64bit), tracktion6/7(32+64bit)
both systems on: macbook pro (late 2009), core 2 duo 3,06 ghz, 4 gb ram, graphic: nvidia geforce 9600M GT 512 MB