Sometimes existing AutoCAD installations just stop working for one reason or the other and will need to be re-installed.  Don't re-install if you don't need to!  Call our technical support Hotline first, to see if you do, in fact, need to re-install your installation of AutoCAD. 

Don't forget that all of these methods require Admin rights to re-install your AutoCAD installation.

#1 - If you have a stand alone license, insert disk #1 and when prompted to fix, re-install, or remove, don't bother with fix, I've never seen it work in my 16 years of using AutoCAD install disks, just use the re-install option.

#2 - If you have a flex license version, go to the Windows Start Bar, Control Panel, and open the Add Remove utility.  Select your AutoCAD installation and fully remove the existing install.  Now, re-install AutoCAD from the license server from your original download location.

#3 - This one is for really bad corruptions where re-installing did not fix the problem, follow the un-install directions from step #2.  In addition to this removal task, delete the folder: C:\Program Files\Common Files\Autodesk Shared, re-start the computer, and then re-install AutoCAD.  Wait, there's one more step!  After the initial install, you need to go to the Autodesk web page that has the latest Service Pack for your install, download and install it! 

Start on the Autodesk home page, under Services and Support pick technical support.  This page has you select the product you need the Service Pack for, pick your version, and click on Data and Downloads.  Finally, select Updates and Service packs, find your version and download the highest number Service Pack available.  You can now install the Service Pack if you have admin rights for your computer.