The reader software is FBReader. It reads FB2 ebooks, but also many other formats. See
FBReader 0.8.4 for the version with menus. It is slow to turn pages, but I continue to use it as my main reader on the iLiad.
There is a problem going from v0.8.14 back to v0.8.4. You need to completely uninstall v0.8.14 first before installing v0.8.4, but there isn't an uninstaller included with 0.8.14. So I did this from a mrxvt window, I think all is required is a single command but I don't remember the exact command I used.
The registry support is a separate issue. If you uninstall 0.8.14, the registry will still want to invoke that version of FBReader for .fb2 files (say). There is a registry installer for 0.8.4 at
FBReader Registry installer for 2.11, but it may not work if the registry already includes entries for 0.8.14. I use FBReader's built in file manager and library, so I have not tried getting the Registry setup for 0.8.4. It should be easier to do now that iliad-regutils is available.