How To Upgrade PGAdmin on Windows
There is not an auto upgarde button built into pgadmin so the latest and greatest will need to be downloaded from the pgadmin site here.
After the file is downloaded then unzip the contents to a folder on your hard drive. There should be two files in the zip file which are a .msi file (used for new installs) and an upgrade.bat file. Double click the upgrade.bat file which will pop up a command prompt and ask if you want to quit or continue. Click enter to continue and the upgrade begins. Depending on what version you are upgrading from and what version you are upgrading to then you may have to reboot. Recently I upgraded from PGAdmin 1.8.2 to PGAdmin 1.8.4 and a reboot was not required.