If you're like us, you do a lot of work on a Mac and send files to a RIP on a PC. I'm lazier than most so, if I want to monitor the job all the way through, I use a program called Microsoft Remote Desktop Connection to control that computer. It's a free download from Microsoft (you have to use WinXP Pro for it to work on the PC.)
I've used other VNC programs - like Chicken of the VNC. MRDC works much faster - I would compare the speed favorably with the speed of using Parallels on an Intel Mac.