a good idea by anagarika to write a guide about this
it is indeed very useful to have all your cabs ready for installation after a new ROM is flashed or after a hard-reset was performed.
Well, most apps come as cabs... but a lot also come as PC Installation files. some extractable, some are not. so...
"How to retrieve CAB Files from PC Installation Files" or "Retrieve CABs"
1. Download the desired EXE installation file.
2. connect your device to your PC using activesync
3. run the installer file and wait for instructions
4. At some point, a message will appear: "Please check your mobile device to see if additional steps are necessary to complete the installation"
5. At this point, you will see the installation screen on your device asking you where to install the app. DO NOT choose.
6. Instead, run your fav file explorer and conduct a search for the cab file (if you know its name) or look for it on your device in /windows/AppMgr or in /Application Data/Volatile. you can also look it up on your PC in /windows/Windows Mobile, /Porgram files/Microsoft Activesync or any other folder which was created by the installation.
7. now you can complete the installation or cancel it.
Remember, every app puts the cab in a different location. this is app dependant.. so you might have to look in all folders mentioned above till you find the cab. fortunately, this is required only once