I stumbled across an interesting item posted a while back by Raymond Chen about the Add/Remove Programs control panel that I wanted to link to here. He describes the algorithm used by the Add/Remove Programs control panel to populate some of the information for each installed application, including estimated size, last used date, frequency of use, etc.
A related article on MSDN describes how Windows Installer will automatically populate some of the registry values used by Add/Remove Programs during installation of an MSI-based setup package. One of the items that is notably absent from the list of entries that Windows Installer populates is the DisplayIcon. This is why you will occasionally see applications in Add/Remove Programs with a completely unrelated icon next to the product name.