The Steam version is cheap enough (I have the original dvd somewhere but spent another £4.49 for their version) and the handy thing is you can delete it and download as many times as you like if modding goes horribly wrong
I am currently running the Steam version in 64bit Windows 10, with GWX 3.0 and a couple of other mods. I have had CTD issues but the 'large address aware' trick that someone suggested has eliminated them completely.