OSX install on Macbook - weird results

[markdavidpro]

I have a .dmg of snow leopard I want to put on my macbook. Don't have any DVD's but I read it's possible to boot it from a USB key.

I install the .dmg file onto the usb key via Disk Utility.

I reboot holding the option key and select the usb key as my option for install.

I run through the process and it installs (takes about 48 minutes).

It then restarts and nothing has changed whatsoever?

I was hoping for a fresh install, with snow leopard. But nothing happens, so what's it doing for that 48 minutes?

I've never done this before so I am probably missing something simple here, please help!

Thanks.
M