The reason I'm asking is that this sounds like a good solution for a silent PC
I thought about that too. But I found it to be cheaper and simpler to install a 2.5" notebook harddrive. I recommend MHT2030AT (30 GB) and MHT2040AT (40 GB) from Fujitsu. Both have only one platter and spin at 4200 revs/min which makes them practically inaudible. As these are not the latest models, you can buy them on eBay at a discount.