If a previous installation of MT4 failed to work on your PC we suggesting reinstalling MT4 into another directory in your PC. 

For example, if the default directory path is c:/programsx86/global, you can change it by clicking “Settings” in the installation setup and create a new path by creating a new folder in the previous directory, for instance c:/programsx86/global/globalprime. 

Alternatively, you can completely uninstall MT4 via Control Panel > Programs > Uninstall Programs > by selecting MT4 there and following the prompts and then run the MT4.exe again.