I've read a bunch of reviews of unsuccessfully updating the software for Ford SYNC. My experience was successful -
I sent away for the new/upgraded SD card for the NAV. Once I received that, I went to Ford site to get the s/w update, and loaded that onto a (brand new) USB device Started the car, turned the radio on/volume low and inserted the USB device (FYI my old SD card was still in its slot in the car at this point) Went to the Settings tool, selected System then Install app. At displayed message I pressed OK The install process began. There was some screens blanking and going through install. IMPORTANT: let it go, it did take quite a while Several service packs were installed (one with 11 updates, one with 10, 6 and 4). Progress bars displayed a line/block as updates continued to be loaded Between each install, I'd see the screen blank out, or SYNC by Microsoft screen appeared. or the home screen displayed
Throughout all this, our car was running. We actually took a drive and there was no apparent interruption in the s/w update progress. Finally after a long time (upwards of 20-30 minutes) we eventually saw a screen with the update message, which was also voice repeated. At that point, we pressed OK and noticed that the background screen still showed a s/w update screen doing 4 of 4. This was followed by an Installation Complete, we pressed OK. Removed the USB device Installed the new SD card for the Nav (A4 is our update) that I previously received by mail Took the USB back to home computer and completed the s/w installation update at the Ford site by "confirming" it.
Best advice I can give is BE Patient, it seems to take an awful long time for the .cab and .zip files to load while you're in the car.