You'd have to use OCR software (Optical Character Recognition). Office
comes with something called Microsoft Document Imaging, which does a
pretty decent job, but it only reads a limited number of graphics
formats (I had to convert jpg's to tif's). It may not have been
installed on your computer by default -- you may have to get out your
Office distribution disk.
My HP all-in-one also came with OCR, but I haven't found a way to get
it to read a file that it didn't just scan itself. There doesn't seem
to be a Browse window attached to the program.