Ok here are a few things to try.
Go into your Windows Vista (I imagine), click on start, then type %appdata% press enter, go into your Apple Computer folder, then iTunes, and delete Device Support if it's there. Uninstall iTunes 7.7 completely. After it is uninstalled, reboot your PC.
Upon reboot, click Start, and type regedit
In regedit, press F3 and type iTunes. for every "hit" you get, delete everything that has iTunes in it, meaning you'll do a combination of pressing F3 then delete, press F3 again, and delete... and so on until iTunes is completely removed.
Reboot again, install iTunes 7.7 again. Then be 100% you have your phone in DFU (You will know by the screen being blank but iTunes still picks it up in restore mode), if you have the iTunes logo with cable on your phone, you are still not in DFU. When you are positive that you are in DFU mode. Close iTunes. Download this file:
http://appldnld.apple.com.edgesuite....7_Restore.ipsw
When it's done, double click that file and cross your fingers!
This may take about 30 mins to do... but hopefully it can unbrick your phone! Let me know if this works for you.