i have downloaded text books that have the extension .PDB , i have tried many viewers even for palm PC , and i couldnot open them ,
Does any one know how to open them or convert them to a common format ?
Since the files you have are supposed to be textbooks, I would assume that the .PDB extension means "Palm Data Base Format" text files. The PDB extension is also used for file formats used for displaying molecule graphic models, and other graphical representations of data. I wouldn't expect a textbook to be one of those formats.
The above program might be worth a try. You also might try looking at one of the files using just a text editor. Sometimes there is ASCII information visible in the data that will tell you what program produced the files. Armed with that information, you can narrow down the search.