Are you logged in under a different account then when you installed apps?

Applications that have been installed as per-user for the current user are displayed in the Add/Remove Programs of the current user. Applications that have been installed per-machine are displayed in the Add/Remove Programs of all users. Applications that have not been installed per-machine, and have only been installed as per-user applications for users other than the current user, do not appear in the Add/Remove Programs of the current user.