If you are having issues uninstalling MSDE because the Change and Remove buttons are greyed out, then you will need to edit the registry.
Go to Start, Run, and type
Then click OK. Now, work through the registry menus to get to the correct one. It is:
Now find the entry that relates to MSDE (HELM)
there's a key called "NoRemove" that will be set to 1. Right-click and choose properties then change it to 0 to make the Remove button appear again.