If you upgraded over ME to XP, that is your problem... What you need to do is wipe your system clean and install XP as a new install. Only way you will cure all your problems.
On a similar note, I just got a cable modem myself and am using XP. XP used to shut down very quickly, before I could turn off the monitor it would be down.. But ever since installing the modem, it shuts down very, very slowly..
Any ideas.