Is 3.5PCV some file name chosen by yourself ?

• if so how did you create it, if it is bookmark content what sort of file is it in firefox bookmark format (.json), or the older text type .html or even a copy of your profile ?

Regarding bookmarks and backing them up have you seen

• (NB remember manually export copies first, to a file of your own naming, restoring from .JSON backups overwrites and looses existing files. )
• Restore bookmarks from backup or move them to another computer
• Boolmarks

I really don't know. While backing up all data (and some settings) I arrived also at Firefox and Thunderbird and found obviously a possibillity to save setting, bookmarks and so, without knowing exactly what the result should be. The result on my back_up disk were 2 files: Firefox 3.6.pcv and Thunderbird 3.1.pcv. I assumed these two files were saving my settings, bookmarks a.s.o. This is all, so I can't answer your question in detail.

The Mozbackup program saves backups in PCV format.
http://mozbackup.jasnapaka.com/support.php

Works wonderfull; Problem solved; Thank you very much.