Thank you for your interest in the Slingbox 500 and for participating in our forum community here! You can actually use the Slingbox 500 with an older non-HD TV. However, you would need to hardwire it to your router and run through Setup on Slingbox.com unless your TV has component capabilities. The only way to utilize the 500's OnScreen Setup and establish WiFi is to have HDMI or component connections.
Here is a comprehensive list of A/V connections:
Hope this helps!
The Sling Moderation Team