I wanted a small, quality, QUIET machine...
I'm going to second the OP in mentioning that the ThinkCentre line is nice and quiet. I'm running a bargain-bin priced A60, and it is whisper quiet compared to the other desktops I've had experience with. Certainly beats custom-built/performances rigs in that regards, but probably is better than many home and business line models as well. Like the OP, the only noise problem I'm having is with the HD seek sounds, although in my case I'll probably upgrade to a larger capacity HD soon and hope that the newer generation 7200 3.5" drives are a little better. I can live with a little HD noise if I have 1 TB of storage.
The Lenovo desktop keyboards are great, which is one reason why I was looking to trade my unused 1 GB of desktop ram for a Lenovo or older IBM keyboard in the marketplace a while back. Very pleased with my ThinkCentre.