dont bother , if they are new to the archos, having 50,000 apps that dont work will only frustrate them, if they know what they are doing, they might not have the same interest as you, so whatever is on it they dont give a crud about.
plus you might want to de-register it, so they have control of the registration, and plug-in $$$ process.
You can always still say it is a possibility to do, and provide explicid instructions on how to accomplish it, or anything else they might wish they knew.
a cleared clean archos is a working archos
any new user would have to get up to speed with the basics first, or they would think it was an inoperable piece of junk. some users might just be happy to watch a bit of media on it, and play some tunes. Some will have it changed so quickly that all the work you did will be dissapeared in seconds.
some will be getting an android phone, and realise the phones limitations, and just be happy that it will do what the phone wont