Tom is right.
In answer to your questions, no you CANNOT modify MBR in ANY way or your encrypted disk won´t be accesible anymore.
Using Windows Recovery console would break MBR and BootGuard access list, and you will lost all your data.
Anyway, is possible that PGP is installed but disk is not encrypted. You can check this if you actually CAN access disk´s data using a different Operating system.
If you can´t access partitions and filesystem is unknown, your disk is encrypted.
In that case, to remove PGP , first you will need to decrypt the disk using Recovery CD. Follow at instructions Tom sent you.
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