Punter,
I have had the same exact problems you had. First my 13gig Toshiba laptop drive started whinning, I didn't even bother with the warranty. Just bought a new one as the noise was driving me nuts.
The new drive, IBM 20gig. And 3 months later, the silent drive was making an even greater whine sound....just drives my ears crazy. I can't use that machine for long because of the noise.
Then I found out. What you want is a fluid bearing drive. I had that on my desktop. Seagate Barracuda 4. It wasn't avaliable in laptops until about 1 month ago, and needless to say, I bought it. It runs silent, and even better still, it runs at the faster 5,400rpm, so everything seems more snappy on my P3 450!
The model you want is IBM GNX series. NOT GN. You want GNX!!! Do a search on pricewatch.com. I bought mine 20gig on googlegear.com. Great price, silent drive, and fast. They have 20,40 and higher capacity. Look it up on IBM. FYI, yeah, I've silenced my desktop as well, with special CPU coolers and fans. Everything is silent in my trading room.