Using target disc mode to access a broken laptop

Question

I'm using a 1.33 15" PB with 10.3.9
and broken early 12" still on 10.2.8
During an attempted repair of the 12" DC in jack, also replacing the broken CD/DVD Drive with a SD using a replacement lower case and screen that still had the screen control? and dc in jack in it, broke the connection for the screen control on the 12" logic board, Thought I had it effectively soldered back on, but appears not. Screen won't light up, But appears to powering up, get the dong and hard drive spins up.
Was told to connect the two units together with firewire and use the Target disc mode to access the data on the broken machine. (which normally needs to be logged into on start up normally, but can't, not being able see the screen)
With the 12" powered up, I restarted the 15" holding the "T" key down and get a screen that has a Yellow "Y" like icon that moves around the screen, "O" with 3 extensions off it, 1 solid and other 2 dashes.
After a minute or so, shut it down, now sure if it was eventually going to work or should have waited longer. or done something else?, Was expecting the normal desktop to show up with some kind of icon for the other computer, then maybe figure out from there how to transfer the data to the new unit.
Have no idea what to do next or what the problem might be, if I'm doing something wrong, or have to change settings somewhere on the 15" before doing it?
This a used unit, with a fresh 10.3 install and upgraded to 10.3.9 Haven't even gone into the system preferences yet and don't know what most of it's for anyway, (Just did the initial set up) or if the 12" has hardware problems still, etc,
Have a USB external HD adapter and can take the HD out of the 12" instead and see If that'll work? But still not sure if I'm going to encounter something else again that's not easy to figure out in order to get the data off it. Transfer it to the 15" or be able to use it on the external drive
Thanks in advance, And hopefully simple instructions....

Answer 1

Thanks, That eventually worked, Oddly produced an open OS 9 Virtual PC 3 Application folder on the 15" desktop that I installed on the 12" long ago and never used before the external drive icon as I named it for the 12" showed up
Clicking on the external hard drive icon had it open the 15" system folder? Hard drive content window (the os 10.3.9 having a different format than what I'm used to seeing)
All the familiar folders from the 12" were there, but the couple times I tried to open one of them, the external hard drive icon and related entire open desktop window, (Hard drive content) disappeared and produced an error message to properly eject the item, But there nothing there to eject anymore, subsequent attempts to get it back failing, But eventually got it up again.
But can't open the 12" mail application to retrieve my old emails and can't seem to find the file to rebuild the 15" mailbox into what I had in my 12" or save/find those emails, but not sure where to look, must be files somewhere for them.
Every time I click on the mail app in the 12" file, it pops down into application bar and disappears. Tried dragging it into the 15"s icon and that not doing anything either. Also dragging it into the app tool bar and trying to open it and it doing nothing, Presume unable to in the later os.
Will this still happen if I take the HD out? and connect with my USB adapter? Need to boot from this? (have no idea how to do that)
Any suggestions on where to find my old mailbox files? Tried opening a number of odd files in the system folder and found nothing in some of them.
I'm presuming this isn't working because it's still an OS X 10.2.8 application But all the other files appear to still be there and think I found the mail before at one time.
Also got an error in iphoto, Can't open it because it needs to be opened in the later version. But found the 12" iphoto file and dragged it to the desktop and took a bit to transfer, so presume I should move it or specific files in it into the 15" iphoto 15" file to retreive the photo's. (and also moved my camera app to reinstall) Same with my itunes which only had a few cd's in it.
The 12" desktop also took a bit to find, but moved that file to the 15" desk top and those files took a little while to transfer. Some of those are MS Word files so also moved the MS Word app and expect to need to reinstall it before trying to open any of those word doc's.
Still wonder why it produced that os 9 as an open folder which was a virtual pc 3 program I never got around to using,