You CAN use the Oleg WL500gp upgrade firmware page. BUT heres what I had to do.
Download the firmware.
On the WL500GP
Press reset for 5 secs.
Unplug cables apart from modem.
Unplug WL500GP power wait 5 secs and plug it in again.
You should see 'DEFAULT' as a wireless network
Connect to DEFAULT
Goto 192.168.1.1 and login, you will notice all settings are wiped - get the firmware upgrade page.
Upload the firmware.
It will say 'FIRMWARE UPGRADING!' you sould not get any diconnected errors.
It will take a few mins to upload - leave it.
You will eventually get the screen of your new firmware. Mine looked just like the old OLEG version - it was a shock when i noticed so many more options.

Im my opinion the rtn firmware for the WL500gp is a major upgrade, and worth installing.
Quote Originally Posted by wpte View Post
ok so these are the steps:
  1. Unplug all the cables of your router
  2. Connect a PC to your router directly via a cable to port1 of the LAN ports
  3. Set the IP of your computer manually to 192.168.1.10
  4. Turn all other network interfaces on your computer off/disable temporarily (sometimes the asus software doesn't like that)
  5. Turn off any firewall temporarily
  6. Unplug the powercord of your router, hold the reset button while plugging the power back in and hold it till the power led starts blinking slowly
  7. Start the asus restoration utility (tftp program) and upload your new firmware file
  8. Wait! just wait till the program is done, sometimes it may even take more time, be patient! (10 minutes is long though)
  9. The router will turn back on! (yay)
  10. On your PC turn back on the other network interfaces, firewall and unset the manual ip
  11. Should be done then huh?