Restricting Internet Access

[OriginalBling]

Hi All,

Greetings for the New Year.

Scenario: 4-6 PC's running Win2k and XP Pro on a LAN. A Win2k PC running ICS to provide Internet access for the clients.
I want to be able at any time to prevent one of the PC's running WinXP from access to the Internet, BUT still allowing that PC access to the local network.

Do i have to use a proxy server software?

any ideas will be much appreciated.

Thanks

JM