Hey welcome to the community Frank!
Unless you have the original disk or made a backup of the initial download, you would need to redownload, install, and activate.
The AutoCAD LT 2011 download can be accessed directly from our Virtual Agent.
Should you run into any activation issues or errors, please contact our License Assistance Team for direct support.
Here to help if additional assistance is needed, otherwise please accept as a solution so that others can benefit from this information!