Originally Posted by tigerszheng
I think it's drm free. but the problem is that I can see those prc files no matter in books , sd card or fbreader.
are there any other problems?
The DR does not show the real content of the SD-card, but extracts information from it and stores it in a database. All the information that you see is coming from the database, even when using the 'SD Card'-view.
The database only contains files with 'known' extensions. The installer for FBReader currently 'installs' the following extensions: [pdb,fb2,zip,rtf,orb,tcr,opf,oebzip,chm] so if FBReader is properly installed you should see files with these extensions (after a restart). Note that prc is currently not in the list of extensions!
The stange thing is that you also do not see the file when using FBReader, are you sure that FBReader supports files of type prc?