I installed win 7 ultimate 64bit without any problem. I was using the RC about a year ago when my computer died, at that time I stop using it and went back to win xp pro 32bit. Just recently my mobo died again, so I went ahead and installed the win 7 64 bit. I was done in 30minutes and have not had problem in over 2months.(except when i shifted my graphic card-loose in the pci e slot- and the computer had problems when I wake it up from screensaver)