Internal hard disk requirements will not allow me to update to Maverick
Usually when there's a problem with upgrading you have to "re-bless" the HDD. This often comes from a permissions problem with something on the HDD. You can open the Disk Utility and do a full permissions check to find any problems.

In my experience I've found the best way to accomplish this is to create a boot-able USB device using something like "Disk Maker X" and then boot from that. Once in the installer Open the Utilities and run Disk Utility from there. This will allow the permissions to be accessed from outside the disk, which helps since you won't have anything dependent on your log in. After the permissions are fully repaired try rebooting to the USB device and re-installing.