Just got GPS working in XP using Carolinas method.
I am posting here to really emphasise that doing this method is best from a clean XP install and making really sure that you do not load any drivers from Dell beforehand for the 5530 - i.e. make sure that the 5530 is totally unconfigured and driverless before doing the manual install of the drivers from the first post. Trying in a previous install I found that no amount of uninstalling of drivers or devices seemed to persuade the Mini to show the GPS port.....so save yourself a lot of grief and frustration and install XP followed straightaway by tackling the 5530 with Carolinas files - it is tedious, but works.
Now happy to say I have full WWAN and GPS in both XP and OSX.
Edit: The ideal way to sort this is actually to add Carolinas Drivers automatically as part of an nLite install process. If you point nLite to the "x86" sub-folder from Carolina during the add driver stage, it accepts them and automatically adds them to the install, so right from first boot you have all the drivers for the 5530 including the gps part already sorted!! That really saves a huge amount of hassle.
Mini 9, 64GB Runcore, 2GB RAM, Triple boot OSX 10.6.3, XP, Ubuntu Netbook Edition (via Wubi)
3G w. A-GPS. BIOS A00, big Chinese battery.