G4 OSX Upgrade - STUMPED

Got an old G5 running Tiger, thought I would upgrade to Snow Leopard via Leopard. Tiger ran fine, used it for a couple weeks as test.

Before. never had an issue, simply ran the discs, ran software update and done.

This time - holy cow, I'm stumped.

Tried the normal way of COMMAND-C and using my system discs - WOULD NOT MOUNT. CD/DVD drive seems to be fine, used it to rip a couple DVD's days before ... Mounted it as a HDD as a Target Disc from my older MCP and loaded it that way.

Ran the Leopard upgrade - installed but all I got was a startup and then the aqua blue screen - then nothing.

Mounted it as a HDD as a Target Disc again - showed up - all files and OS there, ran UTILITY - disc and repair permissions no problem.

Ran SNOW LEOPARD install via Target Disc mode. Said it had to be GUID partitioned. Thought that was weird because I had previously upgraded other macs from Tiger to Snow Leopard with no issues ... but okay, not a lot of files on the G5 so a hassle but no biggie. Wiped it and reformated for GUID.

Ran Snow leopard install. No problem.

Now, all I get the flashing ? that's there's no OS - target mount again, here's where it gets weird.

It doesn't just TARGET MOUNT again (I can see the firewire symbol on the monitor) but it "takes over" my old Macbook Pro - not just as a HDD but as the main OS - is this an issue with firewire 800? It RUNS FINE but I've never heard of this before. And no, I did not switch the startup disc choice.

So, it only seems to run in target disc mode and taking over another computer - what is going on?

Did I miss something?

Thanks.