The Compounder 4 products have been fully tested to work with Windows 7 and Windows 2008 64 bit OSs. However, many of the drivers that you use on the older 32 bit operating systems may not work. These generally include printer drivers and serial to USB drivers. We use USBGEAR (www.coolgear.com) USB to serial drivers. They have worked with all of the 64 bit windows OS that we have tried. Then you need to look at the other software that The Compounder 4 may integrate with (RSI, ERX, QuickBooks financial, QuickBooks Point of Sale, CAM32, Paladin POS, PC Charge, TeleManger, etc. Do these companies offer support for 64 bit OSs. We have been told that PC Charge does not support 64 bit OS.