How to remove the site theme from site settings

After you deployed custom theme by STSDEV and then retract and delete the solution.

You will find it will still exist on site settings-site theme (http://mysharepoint/_layouts/themeweb.aspx)

To remove it, open the file C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\LAYOUTS\1033\SPTHEMES.XML , find the corresponding templates and delete it.

You will see it disappear from the theme management after iisreset.