With the laptop upside down and facing from the front, it is the drive on the right.
There is a youtube video of a guy swapping his main drive on a -a1 with a 160gb intel x-25m.
That is also what I plan to do as soon as I get home!
Be interesting to compare what your performance on that hdd vs the intel.
And no, no raid on the G73, H55 chipset limitation. Me sad, but they had to skip something to get the price that good, wot!