You will have to unplug your webcam from your computer and install the software again.
It is important that you first uninstall your Logitech camera software from your computer.
You will be prompted by the software to plug in your camera, do so that time only.
I am sure your webcam will work fine with Xp , but I will suggest that you make a clean install.
A clean install can possible solve your problem, if your first installation of the software for your webcam didn't install properly or another program in your computers memory was conflicting with it.
You can read more about this procedure at Logitechs site :
http://logitech-en-amr.custhelp.com/app/answers/detail/a_id/620/kw//session/L3NpZC9FS1VNYTl5aw%3D%3DGood luck