DiskWarrior

Both mount and are visible on the desktop or filesystem? Both had OS X installed?

I have 2 internal Serial-ATA disks: Both were checked (with Disk Utility and DiskWarrior) and are OK. But only one of the two disks shows in the Startup Disk list in System Preferences->Startup Disk. Please I need assistance. Sincerely, Sally PowerMac G5 / OS X (V.10.4.11)

You still haven't told us what operating system you are using. If the above suggestion fails and if you are NOT running Leopard (10.5) then I'd recommend using DiskWarrior. (I don't think it's Leopard compatible yet, but check).

Crashed my startup disk on G5 running Tiger. Used Diskwarrior to rebuild directory, but disk was so crashed I couldn't compare the old and new directories. ...

Resolve startup issues and perform disk maintenance with Disk Utility and fsck Mac OS X keyboard shortcuts "Well Known" TCP and UDP ports used by Apple software products Running the Mac OS X maintenance scripts Resolving Disk, Permission, and Cache Corruption

If DiskWarrior and TechTool fail, I hope you had a recent backup. ...

TechTool sucks. Alsoft's DiskWarrior rocks. ...

And Disk Utility and DiskWarrior 3.0.3 can find the disk, but both are saying "Fatal error" and can not do anything to the disk. Is there any other tool I can try or any other suggestions? ...

I vote for DiskWarrior as well. Saved me a few times some data that otherwise would so have been lost. ...

Alsoft's DiskWarrior. It's saved my bacon many times.