First write down the location of the file and the file name (for example, myfile.txt located C:\Documents and Settings\John\My Documents)

Then click Start then Turn Off Computer, then click Restart

While the Computer is booting tap F8 until the Advanced Boot Options Menu Pops up

Choose Safe Mode with Command Prompt and log in normally to a local administrator account. Now Using the command cd (Change directory), change to the directory that you wrote down however make sure to put Quotation Marks around the whole path.

For example:
Cd “C:\Documents and Settings\John\My Documents”

Finally delete the file, using the del (delete) command:

For example
del myfile.txt