can I safely delete thoses entries

I often have those entries after a run of regisltry cleaner:

HKEY_CURRENT_USER\Software\Microsoft\FrontPage\Explorer\Recent Page List\File1,File2.....File8

(Useless empty key)

Also:

HKEY_CURRENT_USER\Software\Microsoft\Windows\Current Version\Explorer\FileExts\DAT_BAK1_with random numbers

(Useless File Extension)

Can they be removed with no harm?

Yes, you can ...

Don't worry, removing those entries will not harm your system nor apllications ...

Anyway, you can always set them back with your backups