Ac1st16.dll is a DLL file (dynamic link library file) that is almost exclusively used by AutoDesk applications. The DLL file is used by AutoDesk applications to view and display complex 2D and 3D drawings. It is also accessed when converting other types of file into AutoDesk files.
AutoDesk Inc. creates and supplies leading CAD software such as AutoCAD, AutoCAD LT, 3ds Max, Inventor, Maya and Revit Architecture. All of these programs may use ac1st16.dll as part of their rendering modules. There are also a number of free DWG file viewers available such as DWG TrueView that also uses ac1st16.dll. Ac1st16.dll is not harmful and is a legitimate file used by applications created by AutoDesk Inc.
If the file ac1st16.dll has been deleted or is either corrupt or damaged, you may see any one of the following error messages:
In most cases ac1st16.dll is loaded when the relevant AutoDesk application is started, in which case you will see a windows error message and the application will fail. In other cases, the application may start normally but then crash at the time the ac1st16.dll file is called. Both circumstances indicate that the file is either damaged or missing.
In most cases, the file ac1st16.dll is installed along with an AutoDesk application such as AutoCAD. If you start receiving errors, then you can run the repair utility that comes with those programs. To invoke the repair facility, go to the "control panel" and choose "add remove programs". Look for the relevant application on the list and you will be given an opportunity to repair or uninstall. Choose "repair" and prepare to have your application CD or DVD ready.
If repairing your AutoDesk application doesn't solve the problem then you can try one of the following solutions: