Im having compatibility issues with snow leopard with some nikon software, and there is no update planned. i therefore need to setup a second partition running leopard for this one piece of software. The issue however is that my machine is a 2009 MBP 2.66 that came with snow leopard. When i try to install it says cannot install on this volume.

Any ideas?

so what is the problem, that you don't have a leopard installation disk?

You cannot install versions of Mac OS X earlier than the one your machine was supplied with.

Your best bet is to identify a replacement for the Nikon software.

Is there a way around it, ie, install on external off another machine and clone across or anything else…

Sure - install Leopard to your external drive (connected to another Mac that will boot to Leopard), then update that bootable drive to latest updates for Leopard. Then, try booting from that drive on your MBP. Should work as that model did come with Leopard before SL was released.
One possibility that may not help, is if the Nikon software is also not working with the MBP hardware, and not just the OS X version. That may be less likely, but still possible...

Ok cool,
its not the hardware, ive spoken to nikon and they made clear to me by the nikon tech support dude that they will not be releasing a SL update for the software…. ignorant people
will carbon copier do the job?