I do NOT think the tuning will work with what MS gave developer’s. Tuning is generally something that happens when developer products begin hitting the real world. I suspect that is when Microsoft expects to be paid for allowing production work to actaully begin.
Microsoft likely also thinks: As a developer on your own workstation you really don’t need to tune. If your software is slow before hitting real world test loads on a setup matching an actual production server — you need to rewrite not tune.
Between these development on your own workstation and the prodcution server, Microsoft does sell Universal Subscription Kits and such which provide special developer copies of OSes and server applications. That is you would set up actual seperate servers similar to the production network to do more elaborate testing against. These softwre products are bascially the same as prodcution software and here you would do tuning when you start sending autmated test data design to look like a full load of real users.
I doubt the XML intereface .dll changed the version of SQL you got. The interface components are pretty standard across versions though as you see certain SQL engine versions simply are unable to use certain features even if the interface components are not there.
You may have to contact someone on the MS usenet forums to find out for sure but — I suspect you got the express version of SQL 2005. Something extra for free. The idea being most development works fine with Express yet most production will need a better version.