I would recommend using windows. I know petrut specifies windows only because he has seen issues using MAC, but not sure why and I concur since I have a macbook pro and had issues. I have windows running in vmware fusion and that seems to work ok, but I went as far as using my work computer (dell) and just downloaded everything and put it on CD so I know I have everything correct.
that being said, my nav program backups are on my MAC OS and I have copied and pasted without issue when using them. it just seemed like the wince hack and stuff I had to make sure was in windows and I have done the same with other NAV programs to make sure they are ok.