"broken folder" icon on start up???

Hello,

Yesterday I had to reinstall Leopard on my Mac.

Everything was going fine until a little while ago I turned on my Mac, and after the startup sound and a few moments of the grey Apple, a No Access symbol appeared - or a "broken folder" icon as they call it in the support pages.

Suffice to say there was a panic after the events of yesterday and I made several attempts to restart, but the "broken folder" icon keeps appearing and noting happens.

I have been able to boot to an external drive (thanks again BDAqua) and I did some googling. I found a thread where a person had this exact problem after a reinstall and was advised to reset the PRAM and given this link http://support.apple.com/kb/TS1892?viewlocale=en_US.

I first tried to reset NVRAM and reselect startup volume, by holding down X on startup. It showed me a message - "efiboot loaded from device.....error loading kernal".

I then tried resetting the PRAM and NVRAM - http://support.apple.com/kb/HT1379?viewlocale=en_US - but this just brought up the "broken folder" icon again - and if left for long enough a grey folder icon with a ? on it begins flashing on the screen.

As best I can tell my only remaining option is to reinstall Leopard.

Unless any of you folks can think of something else for me to try?

I appreciate any help?

Regards