Did you ever find the answer to this problem as I am suffering from it. I haven't slipstreamed WMP10 nor am I attempting to install it during my UA install. I get the pop-up window telling me that SR is turned off and that I will be unable to use SR to return to the version of WMP (9?) that was included with the OS my computer is running. I'm thinking that one of the post SP2 hotfixes is the cause of the problem but I've no idea which. Anyone care to help - please Edit: OK, a more thorough search term has possibly turned up the answer. I'm still looking into it though. Thanks, REB