Capture One 5 is the only version of Capture One that supports a 64 Bit Operating System. If you are running Windows 7 32Bit mode then the same workaround for Capture One 3 in Vista is applicable. http://xchange.phaseone.com/content/sup ... nguageid=1
However, Capture One 3 is certainly not officially supported so there is a possibility for some odd behavior.