I run Vista Home Pro and Cool-er works just fine. I don't see why it would not work with 64bit Vista, it should just read it as a USB storage device. Another option would be the SD card which could be used directly if you have a SD reader on your machine and transfer books that way.
Cool-ers offical website says:
Microsoft® Windows® 2000 with Service Pack 4, Windows XP with Service Pack 2, or Windows Vista® (Home Basic 32-bit and Business 64-bit editions supported)
http://www.coolreaders.com/specifications.asp
Amy