Oh man! You are in for a WORLD of fun, now that you found your NOKIA N800 and need help! You're either going to need to contact Nokia for that FAAAAANTASTIC world-class customer support... or you're going to have to deal with the forums here. :P Fun fun fun.

Alright, setting your expectations aside now... what the last fellow was trying to suggest is that you either crack that puppy's lock code by using ssh--which, if you don't know what it is, you're not likely to have had installed on the darn thing and/or you're going to have to learn how to play with ssh. In either case, that's REEEEEEALLY no fun if you're a Windows user for a myriad of reasons.

The second thing he was suggesting was to outright just erase the thing clean and restore it back to like-new factory OS image using the flash tool. You can find step-by-step info here for your device: http://wiki.maemo.org/Updating_the_t...re#N800.2FN810

If I were you, I'd go for the latter.