Hi.
I quote from this
VideoHelp forum:
1.Change HD
2. Power ON
3.Confirmation of the CPRM ID No. as follows: press ESC then STEREO,
take a note of the 9 digit number, you will need it later( same No. is
on the back of recorder), Exit this mode by pressing CLEAR.
4.Deletion of the CPRM ID No.: press ESC + STEREO, input the same number as the ID number and press STOP.
5. Input of the CPRM ID No. and ID data: press ESC+STEREO, input 9-digit
ID number then press SEARCH to register ID, after this recorder's
display indicates "INSERT ID", open drawer with recorder's OPEN/CLOSE
button and insert ID disc, close. After recorder's display indicates "ID
DATA OK" press CLEAR button.
Do it at your own risk!
I am not sure about maximum hard drive size allowed. The original one was 80GB 3.5'', I think IDE (PATA). In that case better trying with an hard drive that is smaller than 160GB.