Windows Installation Problem

I'm trying to install PostgreSQL 8.2 on a Windows 7 machine.  I had
started with 8.3 but installation stalled and after about 20 minutes I
had to eventually kill it.  When I try and run the 8.2 install, it just
about gets ready and then tells me that another installation is running
(this is after a reboot) and won't continue.

What do I have to do to convince the installer that I'm NOT running
another instance of the install program?  Is something written in the
registry?

len morgan