I've been using Windows 7 x64 for quite a few months now, and there was a bug on the beta version that I thought was gone in the RC, but I see it's still here. Initially I was wondering why the Windows Photo Viewer was so darn sluggish compared to it's counterpart in Vista. From opening images (even small jpgs), to moving the window around, to moving back and forth from one image to the next, it was SLOW. Even small jpgs (say, 200x200px) would take 4 seconds to load or refresh. I discovered the culprit... the Calibrated Display Profile.icc that is generated when you use Windows 7 built in calibration process. When I have this resulting ICC as my monitor's default color profile, Windows Photo Viewer is slow as molasses. If I don't use a profile, or use a hardware generated ICC profile (that I had from my Spyder 2), or any other ICC profile (say sRGB), then once again Windows Photo Viewer is fast as it should be. I've verified this in both the beta x64 and RC x64 on two machines. I have the latest drivers from Nvidia for my 7800gt (same problem with all drivers, even the MS ones).