Using Unlocker you can see which process(es) are using the file. It is also possible that you have to take the ownership of the file first in order to be able to modify/delete it.
How to take ownership:
1. rightclick the file -> Properties
2. Tab Security -> Advanced
3. Tab Owner -> click Edit
4. from the list choose Administrators and click OK
5. Close all settings windows and try again!
It seems that it is impsssible to delete files in 2k8 i guess it is some kind security build-in into it as it was the same in vista? but how can enable delete of files i am useing eraser? http://www.heidi.ie/node/6