According to Steam support, it is not possible for a user to delete or merge a Steam account. It is also impossible to modify an individual Steam ID or Steam account name. But Steam can be removed from a computer using Windows.Continue Reading
Right click the Steam icon in the lower left hand corner of the taskbar and select exit.
Once the control panel is opened, click on programs and features to browse through a list of installed programs. Once Steam is located, right click and select uninstall.
The removal of Steam will take place automatically. Once this process is completed, Steam and any other globally-installed games are removed from the user's computer.