List templates cannot be removed via the Installation Manager. Instead, SharePoint should be used to remove unwanted templates from the template gallery.
1. Access the top-level web site within each Site Collection and/or Web Application, and click Site Settings.
2. Under Galleries, click List Templates.
3. On the List Template Gallery page, click the Edit icon next to the list or library template you want to delete.
4. Select Delete Item from the top of the next page. A confirmation message is displayed.
5. Click OK to proceed. The template is deleted and you are returned to the List Template Gallery page.
If the templates were installed globally, they can be also removed using the STSADM -o deletetemplate command. For more information, see http://technet.microsoft.com/en-us/library/cc288624.aspx.