...as long as you not only erase the visible files, but also do a freespace wipe. However, since you want the whole drive wiped, you may want to use DBAN instead. If you are trying to erase the drive that Eraser is located on, that won't work very well, will it. It can't erase itself or Windows and continue to work.
DBAN boots up from a CD and bypasses the harddrive, so it can remove all information from the harddrive completely. From your description, I'd go with this approach rather than Eraser.