The Belkin F5U109/F5409 will NOT WORK with Windows Vista 64Bit. I will assume that Windows 7 (Ver 6.1) has the same issues. USB to Serial Adapters with the Prolific (PL-2303) and the FTDI FT family Chip Sets have Windows 64Bit Support. From Is the F5U409 USB PDA Adapter compatible with vista 64 bit? ================================================================ Is the F5U409 USB PDA Adapter compatible with vista 64 bit? No, this product is not compatible with vista 64 bit. It is compatible with Vista 32 bit computers. We do however have a similar adapter which is compatible with Vista 64 bit, you can use part F5U257 (USB-to-Serial Adapter). ================================================================