Am I missing something here? I've been using my 8800 as a modem for almost 2 years on my old Stinkpad running Win 2K but I just bought an Asus Eee and I cant get it to work for the life of me. I did happen to notice the 8800 isn't listed as "phones that work" in the How-To but it does work...on Win 2K.
If you have a password on the device you will probably have to use the T-Mobile software. I know on Alltel 8830 and 8330 you can't use the XP dial-up if you have a password... the Alltel software must take it out of unlock mode.