What’s the problem?
Most of applications are pretty ignorant regarding DPI settings (including here a majority of mine applications also). Developers tend to optimize for 96 dpi and leave it at that. With more and more high DPI LCDs it is very hard for users to stay at that setting so lot of them are working on 120%.
On Windows XP this would look very bad if application is not high DPI aware but on Vista they decided to stretch client area of those misbehaving applications to match user selected dpi settings. Form is little bit blurry but it is better than element misplacement and text clippings. Old misbehaving applications look almost decent there.
Problem is that on Vista even applications that took effort to look good on higher DPI settings are affected with that scaling. All that work was done for nothing since Vista makes your application think it is working at 96 dpi.
Telling Vista that I am smart guy
There is a way to let Vista know that we took that additional effort. One just needs to call SetProcessDPIAware API (Vista only!) and Windows will leave us alone to manage our own interface. Since P/Invoke is not my favorite way of doing things from .NET I am happy that there is possibility of embedding it in manifest also.
If you have Visual Studio 2008 embedding this manifest is easy as creating new file but in older versions you will have some more work to do.
Some time later I will lead you through actual creation of well behaving application.