[mstevens]

"installing ... cab files" can mean different things to different people.

It sounds as if you're actually "installing" via ActiveSync, not just copying .cab files from your computer to your phone. If that's the case, you will usually want to install to the device and not to the SD card (one of which should have come with your phone).

For most of us, "installing cabs" is likely to mean copying them to a folder on the SD card then running them from there and installing the program to the device. The reason many of leave the .cab files on the card is because we're flashing junkies and use an automated process or even old-fashioned manual tapping to reinstall programs after flashing a new ROM.