Bitlocker in Windows 7: how to change from USB key to PIN

Found the answer, assuming you have BitLocker up and running, make the changes:

To enable TPM & PIN at boot:

Using the Group Policy Editor (Start -> gpedit.msc and press Enter), go to :

Local Computer Policy > Computer Configuration > Administrative Templates > Windows Components > Bitlocker Drive Encryption > Operating System Drives

and open the key

"Require additional authentication at startup"

Then enable that Key and set "Configure TPM startup Pin:" to "Require startup PIN with TPM"

To set the actual PIN use in a CMD prompt

manage-bde -protectors -add c: -TPMAndPIN 

This will prompt you for a PIN which it then requires you to enter at Boot.

To answer my own question, using the "Manage Bitlocker" option in the control panel allowed me to create a duplicate key onto a USB flash drive and it now allows me to boot from the USB port (the MemoryStick still works as well). I'm not sure exactly what it changed in the boot process, but it worked.