Thanks for using our answers forum! Although xp is no longer supported, this doesn't necessarily mean that it won't work. I actually use the Slingplayer on a PC with xp myself. However, our engineering team will no longer be developing for or fixing any issues with unsupported systems or browsers. With that being said, if you are experiencing trouble, we would ask that you use a supported system and browser. Here's a link to an article from our support page that should help you determine which system and browser to use: What browsers and systems are supported by Watch on Slingbox.com?
Hope this helps!
The Sling Media Moderation Team