To access your XP Computer you need a USB Bluetooth dongle and if you have bluetooth but can't access your computer from the 770 it might be that you need to replace the default MS BT Stack with other drivers.

You can remove the MS BT Stack by (re)moving c:\windows\inf\bth*.*
Don't remove them if you want to use the XP stack in the future... you can backup the files somewhere.

I have installed the SCM drivers for my BT Dongle. You should install the drivers for your BT Dongle or integrated BT Card.

After I removed the MS Stack I could get other services for my BT on XP.

Cheers, Tom