I\'ve looked on the computer summary page which I accessed from my account page, but there isn\'t a merge function there.

The page geophi is referring to, headed computer summary, is a whole page listing information about that computer only - you can drill down to it by clicking on the ID number in the list of your computers. At the bottom, the last item should be a merge option which you can select.

If they are the same computer, you should be able to merge them. Go to the individual computer webpage and at the bottom should be a Merge function that will put them back together.