Can I use an iMac as an external display?

Hi All,

I am looking to purchase my first iMac (one of the current models) but want to check compatibility before committing a sizable chunk of money.

At the moment, I have a windows desktop and a laptop for work. I use a common screen and a DVI switch. What I need to know is can I use the iMac as an external display for the laptop? I will obviously be selling the desktop but unfortunately have to keep the laptop I use for work and don't really have the room to accommodate two VDU's. I have read that there may be a way to do this but it's not that clear and how would I switch between devices (like a DVI switch)?

Many Thanks

Graeme