Well, if you're not afraid of xterms, it's easy enough to flash your 770 from a Windows PC:
- download the Linux flasher from maemo and save it to the root of your C: drive
- download a Knoppix live CD image and burn it (to a RW, if you're cheap :-)
- boot from that CD, type "enter", wait for pretty graphic interface to load
- there should be at least one hard drive icon up left, labeled something like '/dev/hda1'
- note that name, click icon - this "mounts" the drive (ie makes it available as a Linux directory)
- open "root xterm" from the "start menu"
- type 'cd /mnt/hda1' (or whatever the drive name was)
- type 'ls' - you should see the flasher
- type './flasher --enable-rd-mode --enable-usb-host-mode --reboot'
- connect 770 as described before

Voilà - you have root acces AND usb host. Now you can pop the CD from the tray and resume normal XP experience :-)