A customer just installed their Design Suite software for 2015, and received the following error when trying to launch AutoCAD. A quick search yielded results that might end up being quite common.
The error is most likely attributed to an older version of Adobe Acrobat, or maybe even an older Nvidia application. In any case, the error occurs because there is an older program that is using an outdated, unsigned .dll file. The quickest fix is to uninstall the offending application (possibly Adobe Acrobat Pro 9 Extended), and then re-launch AutoCAD 2015. It should work fine now. Now you can re-install the offending program. If you would like more detailed information on the problem, see the following Autodesk forum post here: AutoCAD 2015 (0xc0000142) Error.
If you are unable to determine what the offending program is, you can download and run the Autoruns for Windows, as described in the Up and Ready blog, here. This program will give you the ability to check which programs have either an unsigned or invalid .dll file registered. Simply follow the instructions on the Up and Ready post to determine the culprit and you will be able to get AutoCAD 2015 up and running. You do not need to uninstall AutoCAD 2015, just simply re-launch it after the other program has been uninstalled. After successfully running AutoCAD, you can re-install the offending program, and it should work as before.