Booting from External Hard drive problems

Hi,
I have Snow leopard on a dmg file, that I have restored to a 10gb partition on my external Buffalo Hard drive Specs.

I am trying to install it on my Macbook 2 ghz ( 2 gb ram) running 10.5.8...

I can select it to be the start up drive, but then when the mac restarts it just hangs at the light blue screen, with none of the usual whirring and clicking from the drive that signals its working... I have tried leaving it for three hours... no joy...
Am I looking at a hardware issue here or am I going wrong somewhere...

Thanking you in advance...

Try starting the install from within Leopard, instead of booting from the external.

Hey thanks for the reply, I tried that.. and all seems fine until it restarts and the same thing happens...

Im thinking more and more it could be the harddrive but I just cant work out why it would be an issue!

it could be the partition scheme. In order to boot from an external on an intel based mac, the external needs to be partitioned as a GUID partition table. If it's an apple partition map or a master boot record it wont work. You can change the partition scheme but that requires reformatting the external. In disk utility, in the partitions tab, there is an options button. If you hit that button you can change the partition scheme. It's usually grayed out, but if you change the amount of partitions in the drop down menu (right under where it says volume scheme) it will become clickable. Keep in mind doing this will completely wipe your external and all of its partitions.

Thanks for your help on this, its much appreciated... Ive been trying to do it for hours now!

The disc is partioned with the GUID Partition table

Why not simply install direct from the Snow Leopard DVD or is this an illegal copy from somewhere?

I don't know what his situation is, but when I was installing SL on my brothers mac (I got the family pack), it would spit out the disc halfway through the installation every time. I had to do exactly what the OP is trying to do (restore the disc to an external and install it from there) and it worked like a charm. I don't know why it's not working for him though... And yes, if he doesn't actually own a copy of SL and just downloaded it or something then it is illegal. The disc is $30, it's really not worth pirating it, it's well worth the money.