I had posted this as a response on another forum, but I think it bears repeating as its the ONLY way I can get RSD Lite to work on my Windows 7 machine.
Set RSDLite to run as admin, then use a command console, either powershell or cmd.exe and run it from command line:
"C:\Program Files (x86)\Motorola\RSD Lite\SDL.exe -f xxxx.sbf -t 2"
Where xxx.sbf includes the location and name of the sbf file.
For example, this is what I had to do to get it running under win7 64 bit.
1. Started up powershell.
2. changed directory to where SDL.exe is ("C:\Program Files (x86)\Motorola\RSD Lite\")
3. Renamed my sbf file to 21.sbf and placed it at the root of another partition (try different locations if one doesn't work, preferably at the root of the drive).
4. SDL.exe -f D:\21.sbf -t 2.
5. Let it finish flashing.