Whoah whoah guys, you're going about it all wrong.
Go straight VGA or Component into your monitor. Don't use the PC at all. Don't you have the 30" Apple Display? I'm trying to find the connections on it. Surely it has more than just DVI.
*edit* Also, there are VGA cables that are under $20 that work great. I bought one that comes with an optical cable.
*edit 2* Ok, I can't find the specs for that monitor. If it doesn't have any connections besides DVI, I think you got hosed.
I think the 30" Apple monitor only has two DVI connections. This is because it takes a "dual" connection to display something on the whole monitor (I think). That's the way it was when it was first introduced. But that could easily have changed in the last three years.