Verified answer

there might be some files in your trash that are actually being used therefore they cant be deleted! have you tried restarting your computer and then trying again?

if nothing works you can try downloading this software

http://download.cnet.com/Unlocker/3000-2248_4-1049...

1: run unlocker software

2: manually delete the file

3: if file is not deleted the unlocker software will activate and ask for your permission to delete the file

good luck ;)