Extend windows screen on mac and vice versa

I work on one mac [snow leopard] and windows [XP] I would like to extend my windows screen on the mac or vise versa.

does any one know if there is such a tool?

thanks
Extend windows screen on mac and vice versa
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I work on one mac [snow leopard] and windows [XP] I would like to extend my windows screen on the mac or vise versa.

does any one know if there is such a tool?

thanks