Did you boot from an OS X DVD?
It seems probable that your HD was partitioned with MBR (Master Boot Record) option enabled, instead of "Apple Partition Table". Therefore Mac OS X cannot load from that HD.
You could boot from an OS X boot DVD, and re-partition the HD using the Disk Utility. Remember to enable "Apple Partition Table" as the option. IIRC selecting "default" will give the same result.