Yes, like similar modern units the O450 is a Mass Storage Device as far as Windows is concerned. Make sure you have latest [Only registered and activated users can see links. ] loaded to your PC, connect it via usb cable and you can browse the files on it. The topo will be in Garmin folder and probably it'll be named gmapprom.img.
You can copy it to a usb stick, virtual SD or media card and it'll be seen by BaseCamp to work with on your PC even though it's locked to your Oregon.
If you want to use it with a different unit the img file must be firstly unlocked however: [Only registered and activated users can see links. ].