"Library" folder in USB device

[PCXT]

First of all, thank you for this application.
I've installed Calibre 1.1 in my WinXP machine. It works very well, especially I like the feature with news-to-ebook conversion, but I have a problem with my device.
It's a non-standard old UMPC with no connectivity at all, so I just remove CF card from it and place into USB reader to transfer files. I can make Calibre use the card as a device by User Defined USB driver. In its preferences I can specify a target folder to save converted books (this UMPC likes pure TXT format) and it saves them there properly. But there's one problem:
If I connect the card, I'm getting device's library generated from TXT files all over the card, not only from books folder specified in USB driver's configuration. It means that, for example, readme file of differential equations solver is included as an e-book . I have many TXT files on the card as there are many programs, usually scientific, with large documentation, but these files are in other directories than books folder. How to make Calibre use only a specific folder on a device as library?

Second question: How to use two different devices with User Defined USB driver? I have an old Symbian-based smartphone (Nokia E61), and as it doesn't last long on one battery charge it can display ebooks with images so I'm using it sometimes to read e-books. It will require format different than TXT.

Marek W.

P.S.
One more hint about TXT Converter: There's a combo box to choose target encoding. It shouldn't force an user to guess the proper string for desired codepage. I guessed, cp852 is indeed Codepage 852, when latin2 is a classic Latin-2, not something known as PC-Latin2 but I think these encodings should be at least listed somewhere.

P.P.S.
There's a problem with Polish translation of USB device identifier's discovery procedure. It makes misinformation, as both windows say to make sure that the device is DISconnected. It shouldn't be this way.