I think the best thing you can do, is download the free VMWare Player from here:

http://www.vmware.com/products/player/

download the Ubuntu image (version 6.10, the very latest and bestest) here:

http://www.vmware.com/vmtn/appliances/directory/693

and install both on your computer. There is plenty of documentation on the VMWare pages to get you going.

WMWare is a so-called "virtual machine", it emulates a (nearly) complete PC inside your current operating system (which I guess will be Windows) and will boot the selected image. Once you have Ubuntu running (it's not that different from Windows, but I'd still suggest some learning and playing before attempting to use it to flash your 770) you can download the Linux flasher and OS image to your Linux desktop and follow Nokia's instructions on how to flash from Linux.

The reason this is probably easier for a Linux newbie than using a CD-based Linux distribution, is that most of those don't allow you by default to store new files on your harddisk. Sure, you could use a USB stick, but not everyone has one lying around. The instructions on how to enable your harddisk storage capability are not exactly transparent for newb^H^H^H^Hfresh users.

Besides, VMWare is a great and very efficient way to learn Linux: You don't have to shut down your computer and reboot every time you feel like learning something. And who knows, in a few months you might be one of those who have Windows running in VMWare (note that you can't do that -- legally -- within VMWare Player, but hey...).