Restricting internet Bandwidth to PC’s.

I have a broadband modem connected to a PC running Windows XP and ICS. I want to be able to limit internet bandwidth between PC’s on the internal network – e.g. 30KBps on the XP Box, and the remaining 30KBps (of the 60Kbps link) to the other PC’s.

Is there any software solutions/or configuration scenarios available for this?