Help Network qeury?

I have recently had a new pc installed in the office. it is running windows
Vista home premium.

I need to do two things....

1: delete obsolete network connections on the 2 other office PCs (running
XP)

2: Set up my Vista pc as the host of a new network that allows the two other
PCs to access files on

any advice or pitfalls?

PS: the original network runs through a modem router which has 4 inputs for
the ethernets of the 3 pc to run into.

Cheers in advance.