Download "Unlocker" from CNET http://download.cnet.com/Unlocker/3000-2248_4-10493998.html
After this instal the software. Log back into your admin account (make sure the unlocker program is running after installing it) Right click the pesky file that won't delete and the drop down box will roll out with a new button called "Unlock" It will have a small magic wand with a star icon on it so it shouldnt be hard to locate. Click it and Apply any settings or say Ok that it may prompt you. After this just simply press the delete button on the file you were wanting to delete and it should go away.