The very simplest way to share your folders with an XP machine is to plug the tablet into your XP machine's USB port. The SD card(s) will become visible on your machine as removable storage devices.

"a small form function XP tablet" is a bit of an oxy*****, unfortunately... The reason the tablets don't have the folder sharing capability is because the software required to do it (in this case, Samba) is fairly bulky, and the tablets have very very limited storage space "out of the box". You won't be able to put that kind of functionality on your tablet without some kind of hack to get more space, usually involving cloning your OS to an SD card, or installing Easy Debian and then installing Samba there. (The same goes for printing to a shared Windows printer, by the way)

I have installed Samba in Easy Debian, and you can share folders with Windows computers that way, but it is complicated enough that it is probably better to reconsider your "use case" and see if you can do what you want to do another way.