Hi,
As you already encrpyt the entire hard drive. you need to decrypt the hard disk first before you repartition your hard disk.
"If you want to re-partition a drive that has been encrypted with PGP WDE, you must first decrypt the drive. After you have decrypted the drive, you can then partition the drive and re-encrypt the partition(s). "
Quoted from PGP Guide page 128.
https://symwisedownload.symantec.com/resources/sites/SYMWISE/content/live/DOCUMENTATION/4000/DOC4558/en_US/pgpDesktopWin_1020_usersguide_en.pdf?__gda__=1454542040_2d8cfe4e6d1bd2bca39fb37677ccd817