I'm using VFP 7.0

In a prg/method():
1. How would I go about determining if Internet Explorer is installed on a client's computer?
2. How can I determine what browser windows are open on the client's screen.
Specifically, in my prg/method() I click on a link and even though there is no target associated with the link it still opens another browser window. I need to be able to get access to that window and close it. And since it would open the client's default browser (which may not be IE) would that make a difference?

TIA