I had Building Design Suite 2012 & 13 on my machine. I installed 2014 and then experianced problems with toolbars freezing and not updating in Revit 2012. Fr example I will select a pipe and the toolbar should automaticall update but it doesn't. To fix it I uninstalled 2012, 13 & 14. I tied to reinstall 2012 but the setup says it is installed in my computer. How can I reinstall 2012?
Someon Please help
Revit 2012 and 2013 did not support .NET 4.5. Revit 2014 will install it as prerequisite.
However, you can install service pack and hotfix that can fix this issue.
Read more about it here:http://cad-notes.com/2013/04/revit-ribbon-is-messed-up-after-revit-2014-installed/
For the second problem, did you already uninstall Revit 2012 from program and features?
If you did and still have problem reinstalling it, try using Microsoft FixIt to uninstall it: http://support.microsoft.com/mats/program_install_and_uninstall