Vulnerabilities Of Win XP?

Hi Net Security People
A friend has given me *permission* to "hack" their XP computer. They think
that security is a joke and XP erases all needs for such. Now, I can get their IP,
they are on a highspeed connection 24/7 and run no firewalls at all.
Since they think I am a liar that they are vulnerable, they have asked me to prove it.
I want to take them up on such a challenge. If anyone here has suggestions for just
such a situation, I will post results for you guys... I run Win2Kpro on highspeed conn,,,
-Gecko