I have received a few emails on how to find the downloads for the AutoCAD Service Packs. The AutoCAD Service Packs going back to AutoCAD Release 12 are located on the Autodesk website.
You can get to the AutoCAD or other Autodesk product support by selecting support from the main Autodesk web page www.autodesk.com or going to support.autodesk.com.
Now select the product.
The service packs and updates are located in the section titled "Updates & Service Packs".
Direct Link to AutoCAD Service Pack Page