ipod nano won't restore

Had a series of problems with nano (first model) and decided to restore ipod to factory settings. Laptop froze in the middle of first attempt and had to reboot so ipod was disconnected when said don't disconnect. ipod now had a message on screen saying 'use itunes to restore', have followed instructions to restore, message says 'itunes has detected an ipod in recovery mode. You must restore this ipod before it can be used with iTunes.' so then click ok to restore and appears to do it but comes back to the same message again and just continues in a looop.
Anyone got any ideas how to fix it?