It's a cab file, isn't it? If so, just copy the file to your pocket pc, tap it and it will open up and install.
I, personally, don't like to use hacks unless they are really necessary.....it's just one more thing to remember to do over again if you perform a factory reset.
Unless you have a compelling reason to use an SDHC card with your windows mobile device (like a camera that uses SDHC), I'd return the card and get a plain ole SD card.
Here's a link to the 4 GB SD card I use in my hw6925....been using it now for more than a year with no problems.