File Association conflict

Greetings,

One of my company's land development architects has been having a very
annoying problem with Autocad. He has Land Development 2i installed,
and prefers to use Land Enabled (which I gather is installed with it).
However, when he tries to open projects, the file tries to load with
Land Development. (apparently one requires a file asociation and the
other doesn't)

This started after a couple of days ago he ran land development by
accident when land enabled was already running (apparently a no-no).
We have tried to reinstall AutoCad completely, but this did not fix
the problem. We are now looking at rebuilding his entire OS.

Is there an easier fix than this?

Thanks in advance.