you need to go to disk utility click partition click options and click guid partition. it should be the top option. windows uses master boot record apple does not.
I have already made a new partition in GUID and rebooted my macbook and still got the "Mac OS X can't be downloaded to this computer" error message.
These are the steps i took to end up here.
1. Partitioned 50gb of 250gb in boot camp.
2. without clicking "Go to windows setup" in Bootcamp i reseted my computer and held 'option' and click my windows XP install disc....
3. it asked which partition i wanted to download windows on... it only had one option and didnt show any others so i thought that was the 50gb partition.
4.Without reading the warning signs saying "There is already an operating system downloaded to this partition and downloading 2 on the same partition could make the operating systems function inproperly" i agreed to download...
5. after succecfully downloading xp i rebooted the computer to find that there were no operating systems on my mac that i could access (blank white screen on powering on. held 'option' and no options came up)
6. i realized that I could not go into the operating systems because i effed it up by downloading it to the wrong partition.
7. i fooled around with it for a while with no success then found that the only way i could do ANYTHING was to put in the Windows XP setup disc and go into the setup where it gives me the option to select which partition (it also gives me an option to delete all the data off of the partition)
8. I cleared the partition that had both my mac and Windows Operating systems.
9. Now with a totally whiped hard drive and no partitions made, I put in my original Mac OS X 10.5 install disc and it opens up and ask which language I would like to setup my mac in... I select english and it opens a box and says its downloading and a blue loading bar is up but seconds in the install it says "Mac OS x cann't be intalled on this computer" then gives the options to go to Time Machine or reboot my computer...
10. I got to Time Machine and it says I have no restores.
11. I go to disc utilities and and see I have no partitions made then make a new one in GUID for 249gb...
12. reboot... and the same error comes up...
13. Go back to disc utilities and reformat and reboot and same error... make new GUID partition and reboot and same error!!! PLEASE HELP!!!