Just to add to the previous comments, its always worth having a look for SDHC drivers for your classic Pocket PC. My old HTC Magician, for example, can use SDHC cards up to 32GB, and this device is a 2004 Pocket PC. I know that certain old iPAQs can utilize SDHC drivers to enable them to use high capacity SD cards (greater than 2GB). Caution to backup your device, specifically, the driver that is being replaced. It may be necessary to hard reset the device if the driver fails, as it will disable the memory card altogether...but if you do find a compatible SDHC driver, you will greatly improve your Pocket PC, hence its worth a little effort to try the drivers.
I know that the SDHC driver post on mobilism allowed my rx1955 running wm5 to read and install to a 32gb SDHC card, though the same driver locked up my h1945, h4155 and my h4700. A hard reset had to be performed in order for all three units to see that a SD card was even installed.
I would be extremely interested in knowing where I could get a upgraded SDHC driver for my h4155 that would allow the unit to read any SD card over 2gigs. If you know of a place that has and offers this, please share. It would be greatly appreciated.
Sorry for delay in replying. I regret to say that I do not know of any SDHC drivers specific to the h4155. I am envious of you owning a h4155, it was a groundbreaking iPAQ PDA, and much better than the similar looking rx1955 that I owned, which came out a couple of years later. I've used iPAQs for my work/business, as well as a multimedia/gaming device (akin to an iPOD Touch, years before this came out), my favourite being the hx2000 series. I understand why you are keen on getting this driver, and I'll keep an eye out, but the problem is that with these drivers, its trial and error to obtain a working one, and without a h4155 to hand (regrettably for me), its unlikely I could find out which of the several SDHC drivers I have would work for you. I'll keep my eyes open, and if I see one, of course, I would let you know immediately.
An added thought regarding the h4155 is that it may only be possible to get it to use SDHC cards, if you use a custom ROM, maybe Windows Mobile 5. I know that this may not be appealing to everyone, but devices like the hx4700 can utilise SDHC cards upto 32GB using a custom ROM, with the added benefit of WM5. Pocket PCs with the Windows Mobile 5 operating system are much easier to get them to use SDHC, but if you go older than that (WM2003/WM2003SE), things get a lot harder. The HTC Magician, using WM2003SE, was easy because there is a HTC driver which seems to be universal for HTC Phone Enabled Pocket PCs. Anyway, I hope this helps.