Archos 605 is stuck in Demo mode

Did you try the hidden Reset Button? This is an old unit.

https://www.fixya.com/support/t616253-archos_605_wifi_firmware_disabled

https://forums.techarena.in/operating-systems/1150953.htm

https://www.fixya.com/support/t616253-archos_605_wifi_firmware_disabled

..

Try this:
Power your Archos 101 off by holding the Power Button for 10 seconds (this fully shuts it down).
While holding the Volume + button power it back up (tap power button to start up, hold volume until the tablet enters recovery mode, you'll see a series of choices instead of the demo mode).
Choose the Format System option.
When this process is complete make sure not to select Demo Mode as Android boots and the Archos 101 gets up and running.

Demo software should not be on the device is sold to a customer. Because it is for stores to display them. If you have demo software working on your archos 5 press the power button and hold it for 10 seconds until it shuts off this will reset your device. And it should come up with normal user mode

If you chose any of these options already your Os is gone.. 
try this solution 
I fixed my son's 605 4 GB had Recovery code (104) on it. This might work for other error codes too. These are the steps i followed 
* Use the computer for this process that you always used for this archos Archos should be plugged in to Pc before starting the process.
* Download the firware Upgrade 2.1
* Plug the Archos to Pc 
* When the white option screen comes up pick the format disk
* Wait until all done do not pick any option on archos after format is done Pc should recognize your archos in 5 seconds 
* Put the firmware in root section of the archos not in any folder.
* Safely remove the usb for Archos from your pc first and then unplug the cable.
* Do not pick any option on the Archos screen
* Just turn it off from the power button by holding it until it turns off
* Wait about 5 minutes and plug it back to pc 
* it will come up with white screen again but this time it will start Update you will see the progress bar moving, wait until it is all done, it will shut off. Turn it back on and  your archos will be back to normal

Yes, there is, go to Menu, then i think it is System and towards the bottom there is demo or regular.

hitesh_rao - the reset button is at the bottom by the USB and docking ports. Tiny hole, need a pin or paper clip. Once pressed, just switch it back on.
This may be a stupid question, but when trying to configure the TV IR controller function and entering the relevant codes for my TV's, it asks 'did the TV switch off = Yes/No?'
None of my TV's switch off and then I cannot go any further with the config. Is this right? I have logged this with Archos FOUR times now, and they just respond with 'the controller does not control your TV'. I am fully aware that it is not a TV controller, but then why does it want to switch off my TV during the config? I just want them to answer that question.
Somebody please help!

i have the same problem =(

I got mine out of demo mode. See my blog as to how.
http://thepoetrydude2.blogspot.com

We called tech support and you fix it by doing a reset on the base of the device. We used a paperclip to push the button. Hope this helps!

sent it back to archos with your receipt if less than 1 year and talk to customer service
there is nothingg you can do about it
been there done that.