solution found!!!!!!!!!!!!!!!!!!!!!!!!!!! thank you so much for the support of the Archos team. here is what i did to repair my 504
if your "reset" button doesn't help at all, this is what you'll do.
If you power on the unit by pressing and holding the TV/LCD button and power
button simultaneously the unit will boot into a recovery screen. Once in this
screen choose "Repair Disk" and follow the on screen instructions.
When prompted, please place the following file into the 'root directory' of
the unit:
http://update.archos.com/4/a504/a504_r1.6.53/a504.aosbefore i found this solution, i've already given up on my 504, but now it's back!!!! REBIRTH!!!
thanks once again to Tony H from Archos Technical Support