Internet connection sharing, Slow Clients

Hello all, thanks for taking the time to read my post.

I have a brand new network setup with XP. 5 Systems, one
is connected to DSL via a PPPoE connection (SBC DSL). This
system is XP pro. The remaining systems are XP home ed.
The problem that I am experienceing is that the all
clients, outside of the XP pro (acting as the gateway) is
very slow in connectiong to the interent. I've disabled
the built in fire wall and thats about the only tweak I
have done. I have seen alot of posts on the net in regards
to this problem yet no answers.

I have heard something about tweaking MTU size but I would
appreciate it if some one could give me a black and white
concrete answer.

Thanks much,

John