If you're trying to get newer drives into the old PowerBooks which are equipped with IDE, consider this adapter:

http://www.shopsintech.com/product_info.php?products_id=760&osCsid=b750d12e1ea4eb9de41a5d4793ec7a22



That will get you a modern MSATA solid state hard drive installed anywhere a 2.5" IDE drive would have previously gone. For $16, it seems like a pretty good deal.

MSATA drives are still kind of pricey, but the smaller ones, which is all you'd need in an old Mac, are $55 - $75.