If this is the noticeboard in 7.5 then you could right a query in console to display them and allow the notice board to be opened. Then run the query, click the one you want to remove and right hand click delete (NOT DELETE ALL!)
Sorry should have said we are on 7.4 and the only options we get when right clicking the noticeboard item is open, open in new window and new so i suppose Im looking to get the delete action added to this but unsure of how to do this.
You should be OK Neil. 7.4 has the same sort of system object called a noticeboard, but I'm wasn't certain if that was what you are using. You might even have been using a generic HTML type gadget, or the event older notice board feature of previous versions.
So look in object designer and if you have system/noticeboard item, you should be good to write a query in console which can display all noticeboards. Make sure you set the option in general options at the end that allow you to open the noticeboard. Then select the errant item, right hand click and see if you get the delete! You should, it's just a bit of functionality that happens. If you do, then I declare you officially dangerous :-)