What's always worked for me is first setting up a partition at the front of the hdd for windows, install windows, then you use your linux install cd or livecd, whichever you distro needs to then partition the remaining empty space to however you want, i always do / first, then swap then /home and all the others as extended. When installing linux get grub and it'll normally automatically set up a option for windows. Haven't had a problem yet, though i've barely logged into windows, i keep it for "historical purposes".
Oh and once you have linux set up, NEVER use windows to move partitions around as it writes a new mbr or screws up the boot sectors making it impossible to boot any other os then windows (sometimes not even windows), for partitioning use fdisk or if you want a GUI get qtparted which is like a partition magic clone for linux.
3. The most FRUSTRATING of all the problems is Mozilla behaving slower than a "dial up" when I have a direct connection to the internet. I am having to manually switch between pcs in order to use the internet. I'm over it to say the least.
You have your network card set up properly and all? I've never had any problems using dsl (i have a router that hooks me up). I get max speeds and mozilla works just great. Does this only happen with mozilla or do you have problems with other browsers like konqueror, or any other app that uses internet?