I'll upgrade to Windows 8, and need to decrypt my HD.
It's not possible, because the HD is "only" 99,98% encrypted.
Encryption function properly, but I can't decrypt it.
What can I do?
You should still be able to undo encryption if it's still in the process of encrypting - There's a Pause button at the top of the WDE GUI that then gives you options to decrypt or just stop/pause.
Also be aware that PGP WDE isn't supported under Windows 8, if you didn't know already.
try command line
pgpwde --decrypt --disk 0 -p <passpharse>