I'm using a Quantegy 80 gig firewire external, and it won't mount. Repairing disks comes up as an "invalid b-tree node". I was looking around for some fixes and all I could find was DiskWarrior (90 bucks). As it is my brother's drive and I was just hoping to use the left over space, is there any way to remedy the problem without spending money? If I restore the disk do I lose all data? Thanks.