alright, here we go
So no one has given you the way to do it in terminal, however I think its pretty easy.
Here is what you want to do, find your nasty file/folder on the hard drive. Open Terminal and type 'rm -r' then drag the folder/file that you want to get rid of into the terminal. Then you will see it says 'rm -r /user/blah/crappyfolder'. If it doesn't say this, for the love of god don't push enter. Make sure that it says rm -r then the folder that you want to kill. rm -r will recursively remove everything in the folder that you select, so EVERYTHING, which can be bad if you type the wrong thing.
If it still doesn't let you, then do the same thing but with 'sudo' in front of 'rm -r' this will then ask you for a password, and it is just your admin password.
This will work, just please don' t hit enter if you are not positively sure it is the correct folder/file.
~altair