Photoshop scratch disk question

Hi All,
I do a lot of work with photoshop elements, and currently have an external drive with a 2GB partion as my scratch disk - connected via firewire.
However I am beginning to find this set up a little annoying as it means I am stuck to one location unable to move when using photoshop.
I was thinking about partioning the internal hard drive on my PB instead and so having the scratch disk available wherever and also the transfer speed would be by the Gb instead of 400Mb. (am I right?)
Is it a good idea to partion a hard drive on a portable? is it worth all the hassle of reinstalling and also has anyone had any problems after partioning? like battery life decreasing?
Thanks in advance,
Naj

you seem have to put this question in the software session but fine. well, actually, you don't need to specifically partition you drive for photoshop and just let it choose your start-up disk or other connected drive you choose. but, for external drive, you have to connect while you start up you system. if not, your ps will always switch back to your start-up disk when you start your ps.

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