It comes bundled with the catalyst if you're using AMD/ATi..
hmmm... so, I'm having some issues with mining. I'm setting up a new rig - it's an older system. I purchased a Gigabyte Radeon 7950 and a 600w PSU, I did a fresh install of winxp 32bit (with all 8 million updates), installed all drivers and sdk for the 7950, downloaded cgminer, and I get a file does not exist error for OpenCL.dll when I try to run it ... is there something I'm missing to do?