@
Nepherius - try using
Calibre Portable, if it can do the conversions then you'll know your library is OK, and you'll be able to use the library while you're sorting out the install version.
As well as checking for nasties as suggested by
itimpi, I would also run Windows Update to see if there any missing updates. And have a look in WU history for any failed updates at or about when you installed 0.8.62 - i.e. within the last couple of months.
BR