I bought/downloaded like 250 books (gutenberg.org) for my Kindle Dx. I think has a lot of great free out of copyright books, plus purchased maybe 40 from Amazon. Only like 20% include the title in the file name, the other 80% have titles like aalsdkei.mobi and qeituohq.azw. I need to rename the files so I can only put the files I WANT on my Kindle. How do I open/read the files on my laptop so I can see what file book adlkfjaleja.mobi is so I can rename it?