Before the Storm - 1.12.x to 2.0.1
Once on the mega site just right-click and download the patches you need
This patch allows you to upgrade from Classic to The Burning Crusade, useful if you dont have expansion disks.
Important Notes (Please read and understand before downloading)
With this patch you can patch Classic into The Burning Crusade. However, Please note that if you have a Burning Crusade install disk you should use it after applying this patch to add The Burning Crusade content to your client, then patch as normal.
If you do not use an install disk / ISO and continue to patch as normal, you will be able to access a Mangos Burning Crusade server, BUT you will not have access to Burning Crusade content such as Outlands, nor will you be able to level past 60.
Blizzard had 2 versions of clients during Burning Crusade and Wrath of the Lich King. One was TBC but classic only and the other was full Burning Crusade.
If you do not have an install disk you may search the site for links to torrents or contact MadMax who may be able to direct you.