If these can't solve 503 Error Message issue, appropriate instruction is listed below.
To uninstall a program from Windows 7:
1. Navigate to the Windows start menu by clicking on the Windows logo (Start) button.
2. When the Start Menu opens, select "Control Panel".
3. Depending on your view options either click on "uninstall a program" or "program and features".
4. When the programs and features window opens select the program your want to uninstall from the list and click on the "Uninstall" button.
5. Confirm that you want to uninstall a program by clicking on the "Yes" button.
1.Press Win + R, type service.msc in the search box, clicking OK.
2.On the Service window, find the service you want to uninstall, for example Application Experience, double-click on it and copy its service name - AeLookupSvc.
3.Press Win + R, type cmd in the input box, press enter.
4.Type sc delete AeLookupSvc, press enter.
5.Press F5 to refresh to service window, you will find AeLookupSvc is disappeared now.