To use a Nokia N800 (and most likely the N810) with OS2008 as a USB host you will first need an appropriate cable or adaptor.  I use a L19BT 'USB A (female) to USB A (female)' from Maplin.

To activate host mode as root issue the commands

# echo host > /sys/devices/platform/musb_hdrc/mode
# /usr/sbin/osso-usb-mass-storage-enable.sh

To restore peripheral mode issue the command
# echo peripheral > /sys/devices/platform/musb_hdrc/mode
or
# echo otg > /sys/devices/platform/musb_hdrc/mode
To become the root super-user on any of the Nokia Internet Tablets you must first run

$ sudo gainroot

and before you can do that  the device needs to be in R&D mode, or the gainroot script modified - for which you'll first need to be in R&D mode :-)

More information can be found on these sites

http://maemo.org/community/wiki/Flasher_tool_usage

https://www.muru.com/linux/n800-usb-host/