If you have just tried to install a copy of OSX86, upon rebooting, you may just get a black screen with the following error in the top left corner:
boot0: error
One of the more common reasons for this is because the OSX86 installation was done to a extended partition, instead of a primary partition. OSX86 must be installed on a primary partition for it to boot correctly.
Use a partitioning tool such as GParted Live CD (available from http://gparted.sourceforge.net/) and delete any extended and logical partitions, and install OSX86 again, ensuring it gets installed as a primary partition.
