http://www.moddb.com/mods/median-xl/downloads/median-xl-199b-latest-versionDownload it from there
all it is, is a Patch_d2.mpq file, to replace the regular d2 patch file, in the d2 directory
so what you do is, you take the original diablo 2 patch_d2.mpq file out of your D2 directory, place it somewhere else, i have mine on my desktop, and when the median patch is downloaded, you just place it in the d2 directory.
whenever you want to switch from median/d2, just switch the patch_d2.mpq files accordingly
now, to play median online, you need the server
its east to set up
you download it from here
http://d2maniacs.shbe.org/on the main page that takes you to, scroll to the bottom and click 'Join'
then download the Bnet Gateway Editor, and it has all of the instructions to set it up there
Once you have the median patch_d2.mpq file in your d2 directory, the Gateway editor set to 'D2maniacs', then you can connect to battle.net on median
also once you're done all of that, when you're at the character selection screen, make sure up top that the realm is "Median XL', like for normal d2 its USEast
it starts off as 'Welcome', so you need to make sure you make your char on Median Xl realm