Oh Thank god! I have my blessed Mac Back!
FYI You dont need the startupfiletool anymore. Read the readme file in:
/usr/standalone/i386 on the install cd
It has the instructions to do an fdisk to overwrite the MBR and if needed the partition boot sector too. It's pretty easy. I wouldnt have found that readme without your post though...so thanks a bunch!
Also, I see a lot of people complaining about write problems to the drive...dont forget to umount the disk before writes. This solves the gptsync "data write failed at position 0: Bad file descriptor". Find out what is mounted with the "mount" command.
Disclaimer I accept no responsibilty for a dead hard drive or loss of data but this should work for you i have had the same problem before.
Boot into single user mode (-s at boot prompt) and type the following:
dd if=/usr/standalone/i386/boot1h of=/dev/rdisk bs=512 count=1
/usr/sbin/startupfiletool /dev/rdisk1 /usr/standalone/i386/boot
bless -device /dev/disk0 -setBoot
This assumes you are using the first hard drive.
I have compiled startupfiletool (from Apple's own open source pages) and included it in this post you need to place this file in /usr/sbin.