I encourage you to search the web for this. that on such systems (basically many but the most modern ones) the preconditions of installing OSX (usind GUID partition table) and Win7 or Vista (booting only from MBR-partitioned HDs in case of BIOS. If you have a conventional BIOS managed PC, than Microsoft clearly states that you canNOT boot from a disk that has a GUID partition table (GPT) - rather than a MBR partition table. I involuntarily learnt a lot about these.
One thing is barely mentioned: BIOS and UEFI. REGARDING: BIOS, UEFI systems GUID, MBR et al.
