Reset password on Pix 501 is failing after .bin download

I have a Pix 501 I bought second hand. When I got the pix it was cofigured for the sellers network, I searched and found the cisco procedure to reset the password. When I follow the steps I get to the last part where I’m supposed to get a prompt asking if I want to erase the passwords but instead the Pix stops responding. I’m connecting though Hyperterminal and using a TFTP server to download the .bin to the Pix. Anyone have any ideas?