Network internetconnection problems!!

Hi, up until yesterday everything was fine.. grrrr


PC1 - has a usb adsl modem and I use this to connect to internet... this plus in to a 5 port netwrk hub - runs xp pro sp2

PC2 - general pc running xp pro sp2.... and uses PC1's net connection to view the web.

I've also set them up so that I can see all the files etc..

Now.. mates moved in to my spare room, and i've added his pc to the network to share my web connection...

PC3 - xp home sp??? - no probs connecting this to the network...and running the web share etc


He pops over yesterday afternoon, and switches his pc on.. cant get on the net cos PC1 isent on....

He then switches PC1 on.. and connects up to the Web... checks his email (so he says)... then leaves

I get in.. later... try and connect and the internet logon settings are different...
but.. i manage to connect,
He gets in late lastnight, I'm working away... and he switches his pc on... and limited network connection...

hes done something.. but reckons he hasent..
I've got the network back, and the pc's are talking to each other.. and able to share files... etc... but not the internet connection..

I've been at it for about 5 hours... and I'm just at a loss...

I can ping each pc with no packet loss... from eachmachine.. etc..
but, just cant share the internet..

And I really dont want him back on this machine.. not after this...

any help would be greatly appreciated

Cheers
Jay