Easy way: http://support2.microsoft.com/mats/program_install_and_uninstall/en-us
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall or (HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall)- this is the location where the add remove programs gets populated. If you remove the entry from the registry it would take out the entry. You can delete the key from here as described below and also physically locate and delete the files/folders.
In Registry Editor, locate the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall or HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Uninstall
Each key listed under Uninstall in the left pane of Registry Editor represents a program that is displayed in the Currently installed programs list of the Add or Remove Programs tool.To determine which program that each key represents, click the key, and then view the following values in the details pane on the right: DisplayName: The value data for the DisplayName key is the name that is listed in Add or Remove Programs.
UninstallString: The value data for the UninstallString key is the program that is used to uninstall the program.
After you identify the registry key that represents the program that you removed but which is still displayed in the Currently installed programs list of Add or Remove Programs, right-click the key in the left pane of the Registry Editor window, and then click Delete.
Reboot PC and install current release.