I used to believe that having the pagefile seperate was an advantage and used to run all sorts of tests to try to prove it to myself. Truth is, you actually need a very particular setup to allow this theoretical advantage to show up, and the reason is this.
If you put the pagefile.sys on a seperate partition of your physical windows hard drive, then your reading head in the hard drive is constantly jumping around from the windows bit to the pagefile bit and back again, only actually READING x percent and moving x percent. OK, you say to yourself, i'll put the pagefile on a seperate physical drive as i have two of them and they are the same speed... the problem is they probably are on the same IDE channel though arnt they, so you are still limited but the channel bandwidth even though the drive heads are now free'd up.
What of course you need is a pagefile on a seperate drive AND a seperate IDE channel, and of course not having either of your hard drives sharing IDE channels with anything else, SO... you then need another IDE channel for CD drives etc., and most people only have two.
But if you want a (slight) improvement in speed, then the above is the way to do it. It's gonna cost you though, so probably best to do what i did and buy a better hard drive (i got the Western Digital 7200 with 8MB cache).
Hope that helps.
PS i am not a computer technician, only quite well read, so correct me on the above if you know better...
<A HREF="http://www.anandtech.com/mysystemrig.html?id=19557" target="_new">http://www.anandtech.com/mysystemrig.html?id=19557</A>