1. abbreviated form for Microsoft Windows of any version since 1994 or so.
2. Actually describes the customer experiences of wanting to throw the computer out the window after using it for some time. Similar in use as ‘to google’, thus ‘i want to use the window’.
3. The source of most pain for network engineers due to ancient and inefficient networking protocols. Now recognized as so bad that specialist technologies are available to address the inherent problems of the software see WAAS or Application Accelerators, Load Balancers, et al.
Also, note that Windows product administration is so poor that entire industry exists to fix its problems. To whit, SMS is so hopeless that few people use it.
4. A something used to throw firewalls out of (or through) in times of need.