I assumed that you have a symbian phone and FExplorer installed.  I always count on FExplorer when it comes to eBook manipulation.  For the record, FExplorer v1.17 is a free third party file manager.

I always do this, checking the eBook file and to which application it suits best.  It is as simple as assigning an application to a certain eBook format or file extension.  The process is almost the same with the “right click” – “open with” on computer.  What makes it different on FExplorer is that you are assigning a certain file extension the application it should open permanently not unless you change it or you’ve reformated your symbian phone.

How to do it? (take a look at the screenhots)

• open FExplorer
• go to the file, example “Inday.prc”
• click Option > File > Open with
• choose the application you want for that format
• click Option > Save

Check it if you followed it right, on the FExplorer, go to the file that you’ve previously assigned then click.  If the assigned application opens with that file, you’re doing great.  You can do this to other eBook formats or other file extension name, just make sure to close opened application when not needed otherwise you will encounter memory full (depends on symbian phone you’re using).