I Googled how to make a FSX cab file and was directed back here to a post by Piglet. He uses a program called IZArc. I downloaded it and was able to convert a non-functioning zip file of the gauges into a functioning cab file.
Link to the IZArc program download
http://www.izarc.org/old/IZArc_Setup.exe
If you have the FSX SDK installed you will find the cabdir.exe
file located in the following place:
[your installation drive]\Microsoft Flight Simulator X SDK\SDK\SimObject Creation Kit\Cabdir SDK
Simply drag & drop the folder you want to create a CAB ffor
onto the cabdir.exe file in the above directory.
It will create a CAB file in the directory where the source
folder resides, with the same name as the source folder.
Just as a note, I always leave any XML gauge files that
I de-cab'ed in the panel folder or the main gauge folder.
FSX searches for FOLDERS with the named gauge files
first before it searches for CAB files. Just my personal
preference in eliminating unnecessary FSX 'searches'.
For the same reason I always rename all "aircraft.cfg"
files to "sim.cfg" since that is what FSX searches for first.
Paul