2006 iMac cannot enter boot selection

I purchased an Intel Core Duo 2006 iMac to use as a temporary computer until I can afford to build my own PC in a few months as my only other PC is a PowerMac G5. Now the G5 is faster than the 2006 iMac, but I needed an intel machine so I could run newer programs and got a great deal with this machine. It had Snow Leopard when I got it and it ran okay but a lot of programs, even google chrome don't support x32 Macs anymore. So I installed Windows Vista which is much faster and now I have a lot more modern software I can run. Now the issue is, this mac refuses to load the mouse and keyboard until Windows boots up. Which means I cannot hold alt/option to boot into a DVD. It'll only boot to the hard drive. I tried booting my Tiger disks and my retail 10.6.3 disk to dual boot OS X. It refuses to boot into them automatically. I think my Tiger disks may be PowerPC only though because I can get it to boot in my G5 and my old iBook G4, but not my MacBook. But Snow Leopard is intel only and I know for a fact my disk works. Am I stuck with Windows forever now? Or is there some other voodoo cray cray magic I can do to install Mac OS X another partition?

--I cannot install full bootcamp as it will crash Windows. I don't know why, but it will. So I can't use the BootCamp utility to change the boot device within Windows.