Autodesk licensing issues?

Are you having problems with your 3ds Max or other Autodesk license?  Need to change your serial number to a new one?  Does the program keep giving you a license error when you try to activate?
To reset your serial number so that the program asks you for a new one, start up regedit.  Look in HKLM\SOFWARE\Autodesk\[program name]\[version number] and you’ll see two keys, an “h_register” and l_register.”  If you delete both and restart your program, it will ask you for a new serial number.
If it still fails, look in C:\Documents and Settings\All Users\Application Data\Autodesk\Software Licenses, and the *.dat file inside is your license file.  If you delete it or rename it to something safe (I would just add an underscore to the end), the program will restart the registration process without any erroneous information.  You might have to try this a couple times.