Following these instructions requires/assumes some advanced knowledge, I cannot list everything as I don't have the time. I just thought I'd share my knowledge. Also, should you not follow these instructions well, I cannot be sure what will happen to your computer or device, but all consequences, good or bad, are your own fault. This was done on my own Vista 64 computer using a WUSB600N usb network adapter.

Cheers, T

INSTRUCTIONS:
To install the latest Ralink rt2870 driver (2.3.1 as of today) on vista 64, you need to first install the USB rt2870 on your machine (download from above link), then grab the following files (search under c:\windows\System32):
netr28ux.cat
netr28ux.sys
netr28ux.inf
RaCoInst.dat
RaCoInst.dll

They should all have last modified date of 3/3/2009.

Then add these lines to netr28ux.inf (Place them sequentially at end of list under [Manufacturer]):
;======================================================================
%linksys%       = linksys, NTamd64.6.0
[linksys.NTamd64.6.0]
; DisplayName               Section                 DeviceID
; -----------               -------                 --------
%linksys.DeviceDesc%        = RTWLAN.ndi,           USB\VID_1737&PID_0070
%linksys_AG.DeviceDesc%     = RTWLANH.ndi,          USB\VID_1737&PID_0071
linksys                = "Linksys,a division of Cisco Systems,Inc."
linksys.DeviceDesc        = "Linksys WUSB100 RangePlus Wireless USB Adapter"
linksys_AG.DeviceDesc        = "Linksys WUSB600N Dual-Band Wireless-N USB Network Adapter"
;======================================================================

Put these files in a folder in something called vista64 on your desktop. Then plug in the device. Click, I'd like to locate the driver software, click "NO" I don't have a disk. Then browser for the vista64 folder on your desktop. The driver should then install. You will get an ERROR saying the publisher cannot be verified or something bogus like that. INSTALL ANYWAY. The device should then work properly. It has been for me for the last several minutes!!!

Well no worries. Enjoy the latest driver!

(Mod note: Edited for guideline compliance.)