I am planning on selling my u serve and wondered whether there is anyway to reset it or is it a question of deleting or moving all the files from it?
You can’t factory reset it, so far as I know.
So you have to take the music off using one of the Naim control apps like n-serve or the windows DTC. Or leave the music on it and leave it to the buyer to sort out.
There is no factory reset as such, but you can reset UPnP settings to defaults which will allow a new user to start with a clean sheet.
Strictly speaking you should delete all music files and empty the recycle bin as there are lightly to be rights that you will infringe by passing on any music. (Downloads cannot be deleted via a Naim UI - use a computer.)
In the unlikely event of you having set up a static IP address you should undo this, or the unit won’t work on any other network.
If your selected music store is not on the built in drive, change it to select that. Also delete any backup location and network shares that are listed: probably not essential but it will remove some locations that might confuse the new user as they won’t be accessible.