update 10.6.3 will not install on Windows 7 HP x64

I've tried five times to install the most recent update to my iTunes, new version 10.6.3, and it will not install. Does anyone have a solution to this or maybe I better ask if anyone else has had this problem. I run Win7 HP x64 with a Core i7, 2.5GHz, 12GB RAM, 2TB HDD.