The new version of DISMUI requires .NET 4.0 to run – however if it is required to run it on systems that only have the .NET 2.0 installed you can download the version 3.0 of DISMUI from this blog post.
Please note, that DISMUI 3.0 will no longer be upgraded. It works without any problems on all supported operating system but new features will only be added to the most recent version based on .NET 4.0.