Unless you like to hack the registry, please don't delete a deployment on your network until you are absolutely not using it. For example, if your site is not using any Autodesk 2011 product, then you can delete all the 2011 deployment packages on the server.
It is much easier to not delete the deployment than to hack the registry to a valid location of the software.
Even if you have created a new deployment, hacked the registry and you have duplicated the deployment path, another variable to consider is if you have included Service Packs in the original deployment which can then affect a repair & re-install of the product.
NOTE: This can potentially apply to just regular installed/extracted software as well. i.e. C:\Autodesk
Thanks to Alison Gangler for this suggestion.
An updated solution is noted here: