Secunia is a well regarded Internet security firm, and they've released a free tool that all you Windows folks should take for a spin. It analyzes the applications on your computer, and tells you which ones need security updates.
Even better, it gives you clear instructions on how to get the updates.
It's been in beta for a year and a half, and has nearly a million people using it, so don't worry that you may be the first kid on the block to try it.
Full disclosure: I haven't run this myself (I'm a Linux bigot). However, Secunia has always impressed me as having a clue. Not that this wouldn't be useful for Linux or Mac, but it's much more urgent for Windows.