Refresh the Windows host file without rebooting?

I’m constantly making new virtual hosts on my machine. I try to have one for every project I’ve got going on at any given time. The problem with this is that I’m constantly changing the Windows XP host file…which is a pain because then I have to reboot before the changes become active.

My question is this: Is there another way to refresh the hosts file without rebooting entirely? Maybe a utility out there somewhere, a built in app or a command line option?