There are some firmwire cracks for some DSLRs out there which can enable things like a higher ISO setting - I've no idea if there are any for the D80, and it goes without saying that using firmwire cracks comes with its own risks (not least voiding your camera warranty).
If you can't get the light you need you might well be best to consider investing in lighting of your own - flashes and the like to supplement the low light that you have to work with.