If you are distributing software using .NET then you more than likely have come across the issue of ensuring your clients have the correct version of the .NET framework installed. Microsoft makes that simple enough with bootstrapper installs. However, if you want to keep the amount of bits that your clients download to a minimum so as to encourage your products be more freely distributed, then the following website might help. Scot Hanselman had a recent post where he explained the different sizes of the framework versions and then created a website that detects your framework version and what you will need to download. Could be a useful tool. Check it out here.