Installed both Oracle products package for win32. Unfortunately every login I try doesn't work so I tried to uninstall with remove program on my OS as well as Universal Installer but it can't locate programs anywhere!! Note that I'm working with windows 8... Any idea on how I can solve this problem??
SQL Developer doesn't have an installer - hence you won't find it in Add/Remove programs.
Just nuke the SQL Developer install directory if you want to remove it from Windows 8 (or from any OS for that matter.)
As for your login - who's database is this? Did you try asking 'them' for a proper account to use?