Have you rebooted the machine ? Usually when that happenes to me with applications, I usually reboot the machine, ending all the tasks and recources the program is using. Then when you empty your bin, the files that are being deleted arnt using any of the computers recources.

If that doesent work, try going to your End Task screen and find the task the file is using. End the process, then delete it from the bin.

These 2 ways usually work for me all the time.

Next time you want something uninstalled, just to My Computer, Control Panel, Then Add/Remove Programs, look for Nero and then click delete.