first off make sure that your webserver has write permissions on the DB. On Windoze, IIS runs under the account name IUSR_[name of the server here] ... for instance, i have a web server that is called 'web2' ... hence, the IIS account gets write access to the db is IUSR_WEB2.
"UPDATE Table_Foo SET Field_Bar = 'stuff' WHERE (Some_Thing = 'Other_thing')"
you can even omit the () ...
randal