Unfortunately, we can make no guarantees that the Sales Manager Pro software will work correctly on a Windows 8 machine. You should be able to use the online version of our services on Windows 8, however.
As a follow up, if there is a version of Windows 8 that comes with 'XP Mode' like some versions of Windows 7 did - that's the one you want. Under XP mode the Pro program will not have compatibility issues.