Windows CE is not "****ty" as you say. Just different. Its not a general purpose consumer OS like Windows XP but an embedded OS for use in things like handhelds,factory controlers, gas pumps and yes...CarPCs. (BMW uses it in their iDrive system as well as many other manufacturers such as GM, Acura, etc)
Sadly, there are really no front ends for Windows CE worth mentioning. Especially x86. This is mainly because WinCE is just not a popular choice for the CarPC community as its not exactly the easier OS to get started with. This has nothing to do with the capabilities of the OS. CE in fact has more and better navigation software than even desktop Windows XP (like TomTom) and in my opinion it should be the de-facto standard...but, alas, it is not. I'm hoping things will look up some day. I actually "found" a navigation solution for x86 Windows CE that someone sent me from this aftermarket WinCE carputer/nav system they bought while in china.
You of course can't use Windows Desktop programs on a default WinCE system, however the odd thing about this AMD device is that a lot of sites that list specs for it say that it comes with some kind of AMD developed "XP Extensions for CE" compatability layer for x86 Windows CE. I'd kill for the dll files of this layer! If you can provide me with an image of your device's HD, I would be quite happy. It would be quite interesting to try on other x86 Windows CE devices such as thin clients, CarPCs, etc.
Based on various google and eBay searchs, I think there may actually be 2 different variations of the AMD presidian WinCE device:
1. Those that are "locked" from installing 3rd party programs. It seems these may have been sold in some third world countries by telecoms and users had to pay a monthly fee to "rent" the device and use it basicly for for internet access and typing documents with TextMaker and PlanMaker.
2. Those that are fully open and should at least run the (limited) amount of x86 Windows CE software available.
Being that I am such an advocate of the Windows CE OS and I feel kinda sorry for the availability/selection of software on the x86 Windows CE processor type, (Consumer CE apps are ARM only today) I have compiled an extensive list of x86 Windows CE software programs as I've come across over time on google, etc. In addition to commercial programs, I also search the web quite often to find as many Open source Windows CE programs as possible. I already have many useful types of software such as emulators (MorphGear, GNUBoy), Video Players like TCPMP, etc. compiled for the x86 processor type. There are many open source programs for Windows CE based Pocket PCs and many will run on x86 with just a simple switch of the processor type in the compiler.
In addition to native apps, you should also be able to run most .NET Compact Framework programs written for Pocket PCs and other WinCE handhelds on x86 WinCE devices such as your presidian.
I hope this has helped to clear a few things up regarding your device.