As you bought this AP (not a new one), I would suggest you reset it to the default configuration and reload the AP image using MODE button (Link here):
Resetting to the Default Configuration
If you forget the password
that allows you to configure the access point, you may need to
completely reset the configuration. You can use the MODE button on the
access point or the web-browser interface.
Note: The following steps reset all configuration settings to factory
defaults, including passwords, WEP keys, the IP address, and the SSID.
Using the MODE Button
Follow these steps to delete the current configuration and return all access point settings to the factory defaults using the MODE button:
Step 1: Open the access point cover
Step 2: Disconnect power (the power jack for
external power or the Ethernet cable for in-line power) from the
Step 3: Press and hold the MODE button while you
reconnect power to the access point.
Step 4: Hold the MODE button
until the Ethernet LED turns an amber color (approximately 2 to 3
seconds), and release the button.
Step 5: After the access point
reboots, you must reconfigure the access point by using the Web
browser interface, the Telnet interface, or Cisco IOS commands.
Note The access point is configured with the factory default values
including the IP address (set to receive an IP address using DHCP).
Ctrl + Breakor hiting ESC several times during its booting process.