Vista Beta 2 is a free download from Microsoft right now. I too was faced with the challenge of moving a several gig image from the upstairs family computer to my personal testing computer downstairs, and then installing it (I don't have a DVD burner either). The downstairs computer had 2 hard drives, and one had XP on it, so I just moved the image over the network to the XP side of the downstairs computer, then installed [free] daemon tools (which will emulate a drive with an image), then installed it from the XP side over to the second hard drive. If you're limited to one hard drive, this could be accomplished with a 3 gig XP partition, and a (remainder of hard drive) Vista partition. You might be able to do it all in one partition, but I don't know if that would work out. By the way, Daemon tools is amazingly helpful for many purposes, but when installing it, make sure that you uncheck the 'install whatever toolbar to launch targeted ads' button. Don't worry though, if you uncheck that (and it's blatently labeled), it won't load the toolbar (or any other adware) onto your computer.
-:-Mitchell