You could do this:

• Turn-off the CPU.
• Take your MMC from the CPU
• Slot the MMC in a PG (USB burner on laptop/PC).
• In the SIMATIC Manager select "File".
• Select "S7-Memory Card"    ==>    "Delete..."
• Slot the MMC again in the CPU and turn it on.
• Then do the following to change the password protection in your CPU.

Open the properties of your CPU in the hardware configuration.
Change to the tab protection, and parameterize the first (no protection) protection level.

Load your HW Configuration and Program into the CPU.