can't boot from Ext. FireWire HD

[paragon]

I am running Lion on a MacBook 2 GHz Intel Core 2 Duo, I have a 2 TB FireWire HD (partitioned into 3 in GUID) connected to it. I just installed a Snow Leopard on one of the partitions and hoped to boot from it but alas nope, it won't show up when I press "option" on startup but it does show up on the startup disk manager in sys' pref'
Any ideas?

[paragon]

I just connected that Ext. HD to my wife's macbook pro running SL and tried to boot from it and voila it worked just fine, it seems to me that Lion behaves exactly as in the wiled it kills all competition

[DeltaMac]

Which MacBook do you have? There's 5 different MacBook models with 2.0 GHz Core2Duo.

What happens if you choose the 10.6 boot in Startup Disk, then try to restart...
Try updating the 10.6 install with software update.
Do that update to 10.6.8, etc, on a different Mac, if you need to.

I have an external with 10.5, 10.6 and 10.7 OS X installers, and also fully installed OS X partitions for 10.5.8, 10.6.8, and 10.7.4, and have no problems whatsoever choosing and booting to any of those.

If you still can't get the SL boot on your own MacBook, try a USB connection (be sure to disconnect any Firewire connections on the WD drive - you can't use both at the same time.)

Another possible fix - boot to your Lion MacBook. Plug in your external, then run Disk Utility, and run Repair Disk, once after selecting the 2 TB WD drive, and again after selecting the Snow Leopard partition. Repair Disk will perform different tests, depending on what you have selected.

[paragon]

it just restart into lion,
how can I know which model I have? it is a1181 (late 2006) that is all I know.

the SL is now up to date and still nothing.
do you connect your dive with all those OSs with a fire wire or USB?

[DeltaMac]

I have two different drives with those multiple partitions. One is Firewire or USB, formatted Apple Partition Map, used mostly with PPC Macs, but also will boot Intel Macs. The other is USB only. That one will only boot Intel Macs, as it is formatted GUID.

Late 2006 is all you need to know about which Macbook model you have. You can also verify that in your System Profiler (System Information in Lion), where you can see that the Model Identifier should be MacBook2,1

I have the Maccabee TM partition figured out (Time Machine backup), but is there a system on the Radmigon partition?
I would probably try reinstalling Snow Leopard on your external drive, while it is connected to your own MacBook.
Did you try the Disk Utility/Repair Disk, after selecting the Snow Leopard partition, and also after selecting the 2 TB WD? That would be running Repair Disk twice, as a minimum.

[paragon]

on radmigon there are only media.
it is booting with the usb cable but not with the fire wire.
however, I have decided to keep on with lion. thanks for help.