Start with the following:
First, be sure your antivirus software has the latest definitions and run a
virus scan.
Second, download, install and run Ad Aware:
www.lavasoftusa.com
Note: you should always be well backed up before running an application of
this type.
If both come up clear, open Control Panel, open sounds and audio devices, go
to the Sounds tab. Now, this is where it gets tricky, you'll have to select
each one individually and see if there is some weird sound associated with
it. Select the item, just below the Program Events, a box will appear
called "Sounds," there is a right point error next to it, click it to reveal
the sound. While they will usually point to Windows system sounds, you
might find one that is called cat, cats or meow or it might be a system
sound that has been appropriated by something else so click each sound to
test and see if one them meows. If you find it, try associating the event
with one of the other sounds on your system.