Message on LaCie Hard drive says Hard Drive is... I have three items backed up on the LaCie D2

Question

I have three items backed up on the LaCie D2 hard drive, with a total of about 15 Gb. But I keep getting the message that the hard drive is full. When I attempt to trash the last back up of my computer, there are about 20 000 items (!- I must have copied all what was in my Trash onto the Hard Drive). During the emptying Trach routine, I get a message saying unable to remove FMStrs.dis. Neither my Finder nor my Spotlight is able to find this file on my computer. Clearly I have done something very stupid here. Can you get me out this trash I have buried myself in? Thanks! Martin Dives