Haven't noticed the CPU-hogging myself, then again I've no huge PSTs.
As another poster pointed out, the indexing service will take a long time to perform the initial indexing. Once that's done it will require much less CPU and disk I/O as it simply updates the index incrementally.
If you leave the indexer to its task for long enough then it should eventually finish up its task and stop using the CPU (completely). Perhaps you could leave it on overnight and see if that allows it sufficient time to finish? Repeatedly stopping and starting the indexer probably hurts its efficiency.
From your problem description I assume your laptop is fairly far down the low end. It's a possibility, then, that it's simply underspecified to run Windows Search. Windows 7 isn't exactly lightweight to begin with even though it performs better than XP on modern hardware (in my experience). May I ask for the specs? I own a laptop that's about four years old and it runs Windows 7 just fine, search and all.
You need not worry about running at 100% CPU for a long time. As long as all fans are working, no vents are blocked and the ambient temperature is not too high then it should be fine. I've had ThinkPads inside closets running at 100% CPU for months will no ill effects. (Don't ask me why.)