My machine is very slow especially at startup, many tools uses my tray and they provide no way to delete. Even if I tried to uninstall, some refused!

Here how to get rid of them, at least the annoying. Open Start Menu, in the Run editor, type RegEdit.exe and hit enter. (very long way to say run regedit!)
Browse the keys to reach the following path:
HKEY_LOCAL_MACHINESOFTWAREMicrosoftWindowsCurrentVersionRun

Review the and make sure to remove only unwanted entries. Be careful, registery changes are not for beginner users.