Edit: When I say this doesn’t work with Windows 7, I mean that I had issues with Win7 x64. There are reports that it works fine in 32 bit version, and that it might work with the 64bit version if you disable driver signing.
I just successfully upgraded my HTC Touch Dual (known as NIKE in other regions) from windows mobile 6.0 to 6.5. It took me the better part of 6 hours to fully research and figure out how to do it. So to help the next person out, here is how to do it (entire process will take about 20minutes)
Note: This is the process of updating a HTC Touch dual. Updating other phone models is very similar. Just find your specific version of Soft SPL, Hard SPL & ROM images. Go to http://forum.xda-developers.com to find your model phone.
BIG WARNING: You will need WinXP to do this. IT DOES NOT WORK WITH VISTA OF WIN7. I wasted 5 hours at this point when i bricked my mobile because it will not flash correctly. So find an old WinXP machine just while you are doing this. Also you may want to backup all your existing data. I take no responsibility if you brick your phone.