You said "when I try to install a purchased version it wont download". That doesn't make any sense. It doesn't matter what's installed on your computer. You should still be able to download the program. I can understand if it won't install, but downloading shouldn't be an issue.

 

Normally I would suggest running a repair or reinstall the program and then uninstall, but since this was a trial version, you won't be able to do that. I think you will need to contact Autodesk and ask them how to remove the trial software from your computer.

 

One other option would be to http://www.associatedcontent.com/article/17056/system_restore_can_roll_back_computer.html?cat=15" rel="nofollow - use System Restore to roll back to a time before you tried to remove the trial software . But, you will need to have set a restore point prior to removal of the program. I'm guessing you probably didn't do that, so this may not be a viable option for you at this point, but it is something to keep in mind. Always set a restore point before you do something like installing or uninstalling a program.