I think he wants the root password so he doesn't have to reinstall. To get the root password you could just use a live distro like knoppix or something like gentoo to mount the drive then copy the /etc/shadow file to a disk and crack it or modify it.
As far as your modem being detected, if it's a winmodem it most likely won't be detected but that all depends on what distro you use. Fedora or SuSE or a distro like that might detect it, otherwise you'll need to get some special drivers Here
Just follow thier instructions and installing it should be easy. Once again it all depends on what distro you use.