Uninstalled .NET Framework and reinstalled and programs won’t run

I deleted .net framework 1, 2, 3, 3.5 in the Add/Remove window and reinstalled NET. Framework 3.5 which installed all of the version. Now there are many issues to resolve, for example Preview in Explorer gives a Fatal Execution engine error, and application has generated and excetption….etc. I tried to uninstall .net framework packages but they will not uninstall. In fact NO program will uninstall. Certain other programs like Palm Pilot desktop will not work. Scripts will not run, etc. How do I resolve this .NET Frame work issue? What are my options?

Thanks

Doug