This card does, indeed, work with Vista / Win2k8 x64. The driver was not installed by default, though. You need to go to Ralink's website and get the driver for RT61 chipset for Windows.
Support Website: Direct Link:
Then you have to install the drivers. They won't work automatically but they'll appear in program files\Ralink. You have to force device manager to use the Ralink drivers:
Device manager->Update Driver Software->Browse...->Let me pick...->Have Disk...->Browse to the Drivers in program files\Ralink\Drivers->Choose Ralink RT61 MIMO Wireless LAN Card Driver
EDIT: You
CAN NOT let Windows try to search for the driver from the list, because Windows will not detect it on its own. You
MUST manually select the driver because Windows does not know it is the correct driver. Also be sure to select the exact driver I listed (Ralink RT61 MIMO Wireless LAN Card Driver) if you have this exact card, the AWLH5026. If you choose the wrong driver Windows will try to install it anyway, and it may have unexpected or undesired results. I cannot be held responsible if you mess something up