Note: This information applied to an older version of the forum software, and is no longer accurate.
If you go to the full edit (not quick edit) page for the first post in the thread you can delete it there. I think there's a checkbox for it. Of course you can also PM a mod or report the thread if you want us to do it for you.
If you're using the UK forum the edit functionality rarely works. You'd have to go to tomshardware.com instead.