I can't tell if it works on 64bit Windows, as I don't own a 64bit computer (yet). Feel free to try it out, from what I gather, it should be even safer and easier to try, as you would then only have to change the flag in the Poser executable and notthing in XP's boot flags. In fact, you wouldn't even need to reboot, you would just need to call editbin /LARGEADDRESSAWARE C:pathtoposerPoser.exe (AFTER you made a backup copy of Poser.exe). editbin.exe comes with Visual Studio, if you don't own it, Visual C++ Express Edition is a free download from Microsoft.