The danish computer security service provider has released Secunia PSI (Personal Software Inspector) version 1.0 after a 17 month beta test period. With this software you can identify unpatched and old software that makes your Windows system vulnerable to attacks. Though this is not a complete indicator, Secunia can identify currently about 5.500 applications. This is quite a lot and the list continues to grow.
I also tested and still use Secunia PSI. It offers a good overview what software needs updates, patches, etc. and speeds those up by providing a button that points to the right update sites. It is so easy that I can recommend it for everyone that want to have