BUG #4938: upgrade to 8.4 issue

The following bug has been logged online:

Bug reference:      4938
Logged by:          Anders Edstrom
Email address:      ae58@yahoo.com
PostgreSQL version: 8.3
Operating system:   Windows Vista
Description:        upgrade to 8.4 issue
Details:

Hi,

When I run the installation of postgresql 8.4 I'm prompted for password.
When I issue the password I have for 8.3 (=dbpass)I get an error message
"invalid password" ??

I don't understand how that is possible since its the only password I have
?

How can I reset the password so I can get the postgresql up and working
again, i.e. I have also now tried to uninstall 8.3 but get the same message
of invalid password?

Help please ...

Best regards,
Anders