BLU-RAY PLAYER/BURNER COMPATIBILITY?

I have a bog standard Packard Bell desktop computer running Windows XP. I bought an external USB Blu-Ray player/burner. It will play DVDs, but not Blu-Ray. When I put a Blu-Ray disc in and try to run it is tells me that either the disc is corrupt (it isn't) or it is running on an incompatible system. Any geeks out there want a quick ten points - just tell me what I have to do next!