Thank you for your response. It does help.
Obviously, I was wrong. The problem was occurring for a coworker. When he moved to a 64 bit machine, ESRIRegAsm was failing. I looked at the environment variables and incorrectly jumped to the conclusion that this was the heart of the issue.
For some reason, it started working after we created the symbolic link. In hindsight, the link was not necessary and the illusive problem was elsewhere.