When ever one tries to install a multiboot OSX Window box, you are most likely to run into the boot0:error, or a b0 error. what this means is that the partition that you intend to boot into did not have the active flag set. Most of these errors arise after you have installed 2 systems and it wouldn't boot into either or both. This can be easily fixed by the following steps
1. Boot with mac OSX boot disc
2. Goto Utilities and enter Terminal
3. in the terminal type
Make a note of which disk has the partitions(rdisk0, rdisk1, etc)
fdisk -e /dev/rdisk0
you might see the MBR error, don't worry about it.
and you should see all your partitions. At this point you would want to figure out which partitions you want to boot into first. If you have 2 partitions then flag the one you want to be primary last.
For example, you have 2 partitions, 1 and 2.Partition 2 holds windows 7 and 1 holds OSX Snow Leopard. You want to boot into OSX boot loader to choose which parition to boot, in this case you want to flag the windows partition active first, then flag the OSX partition active,
6. so you would type
This would fix your problem, eject your CD and reboot.