There isn't any official slip streamed version of Win 7.
But, it doesn't mean that you can legally control the installation of slipstream of Win 7.
Read here by MS: http://answers.microsoft.com/en-us/wind ... 8446311c34
You can use VLITE to create your own legit image of slipstream version of Win 7. http://www.vlite.net/download.html
This shows as Vista, but can be used on Win 7, after all, Win 7 is actually Vista, just better.