When you install a second time GECAMed, you may have a problem with a user in postgresSql. First remove the POstgreSQL Database from your system via the Add&Remove Programs in the windows control panel.
Afterwards you have to delete the user postgres_gecamed in Windows:
Local Users and Groups
Open a command window (CMD) using the “Start ⇒ Run” menue entry. Then type the following command and execute it by hitting <enter>.
(Windows XP Home versions does not have the tool described above)
net user postgres_gecamed /delete
This might not work an Windows Vista!!! If you are having problems with Vista and removing the user, you either have to know where to remove users in your Vista or, disable User Account Control (UAC) feature. And afterwards, retry the command above.