1. Try boot from your install DVD and delete the file from command line
2. Download an eval (45 days) copy of cfi Shelltoys from
http://www.cfishelltoys.com/ - it's safe, I've used for 5+ years on XP, Vista & Seven - it adds a sub menu to your Windows Explorer right click menu
Use its Delete on Reboot option - this has worked for me on files that I couldn't remove with unlocker
I hasten to add this was on other peoples computers, the problem were probably caused by games, although in one instance it was definitely the Bonjour software that came via an early version of ITunes.
BR