Sorry for the late reply.
Is this hanging when you are just opening Autocad on it's own, or when you click on a drawing file to open it?
And is it with just one drawing or every drawing that you try?
If it's just the one drawing then it would suggest that there is something wrong with that particular drawing and there are a few things we can try.
If it's with every drawing then it would suggest that its the Autocad itself that is faulty and it may need to be repaired/restored.
The first thing to try in that case would be to restore Autocad to the default settings and see if this cures the problem.
OOPs, you did say Acad 2005 in which case its a bit more difficult to reset to defaults, including a registry edit.
Back up before doing this, it tells you how in step 2 of this guide to resetting Autocad before version 2011: