If I'm not mistaken, not only is that particular file hidden, but it's read-only as well. Ever since the DOS days, you had remove both the hidden and read-only simultaneously (and in most occasions, you'll have to remove system as well). If you didn't, the attributes won't change. So the command line would be

ATTRIB -R -S -H filename

The ATTRIB comand also takes the flag /S which will apply the changes to the files in the subdirectories as well. So

ATTRIB -R -S -H *.*

will remove read-only, system and hidden attributes in the current directory as well as any in subdirectories.