My windows installer is not working

Hi folks,
Windows Installer keeps trying to load a program (Hp Camera software) which I don't have any more. No Disc, and the files cannot be found on my hard drive.( a .MSI file).
I went to add/remove programs and get the same message, every time I open a program or go online or if the computer is just sitting. Windows installer pops-up, asking for the source disc or file. How can I stop this?
Thanks.
