DirectX 10.1 Where do I get it?

I have a Sapphire Radeon HD 4550 512MB Video card and It supports DirectX 10.1. In the dxdiag thingy on my vista, it shows I still have version 10. I already downloaded vista 32bit service pack 1 a long time ago, but I didnt even have a directX 10 card. So now where am I supposed to get DirectX 10.1? I cant find a download or anything. I tried running my webDX updater thingy thing and it doesnt update to 10.1. Im still stuck at DX10, a little help?