When you are running a Mac with Parallels to run your Autodesk product [AutoCAD], we only support the default setup of Parallels and Windows. The instructions for this default setup is noted here:
How to install Windows on Mac using Parallels Desktop?
http://kb.parallels.com/ca/4729
Setting Parallels Desktop to run Windows from the Boot Camp partition is not supported and the instructions for this setup is noted on Page 16 here:
Getting_Started_With_Parallels_Desktop.pdf
The reason for this is that the Autodesk product [AutoCAD], is registered to the Windows hard drive partition in Boot Camp. When you install Parallels afterwards and try to run the Autodesk product , it is trying to read the registration information on the Mac hard drive partition and it will error out.

To resolve this issue, please follow the following instructions:
1. Restart your Mac in Boot Camp so that you are running in the Windows partition.
2. You will need to show hidden files on Windows.
http://windows.microsoft.com/en-us/windows7/Show-hidden-files
3. Backup and then delete the following files:
Windows 7
C:\ProgramData\FLEXnet\adskflex_00691b00_tsf.data
C:\ProgramData\FLEXnet\adskflex_00691b00_tsf.data_backup.001
4. Create a new user Administrator account called "Autodesk".
Select the Video: My computer is in a Workgroup
http://windows.microsoft.com/en-IN/windows7/Create-a-user-account
5. Logout of the current account and login to "Autodesk".
6. Launch AutoCAD and let it activate. If it doesn't activate automatically, please check out this post:
http://upandready.typepad.com/up_and_ready/2012/05/general-licensing-getting-an-activation-code-manually.html
7. Please logout of the "Autodesk" account and log back into the orginal account and launch your Autodesk product [AutoCAD].