Your posts are kind of vague as to what you are trying to do. Hopefully I can help out. If you connect your Gigabeat to your computer with the AC adapter and USB plugged in, you should see it show up in Windows Explorer. Make sure you aren't using the cradle. Make sure you (as you have already mentioned) click "show hidden files," uncheck "hide extensions for known file types," and uncheck "hide protected operating system files" under Windows Explorer -> Tools -> Folder Options -> View Tab.
So if you navigate to K:\GBSYSTEM\FWIMG. (K:\ being the drive letter of your Gigabeat.) Inside that folder you should see the FWIMG01.DAT.