We need more details. You realize of course there are MANY different Archos models. And you provide in your post is inadequate detail. Provide current model and which firmware to which unit. This will help provide better assistance.
I'm going to post a link in a new thread for upgrading from Android 2.1 -> 2.2, as well as installing Google Market (the version that works on Froyo/2.2 - the Google Market link that many people have posted in the past is only for 2.1)
See my other thread.