Hello Pelangi,
I apologize for not getting back to you sooner on this post. I checked my current installation for the Engine (both the Binary version installed through the Launcher as well as the version I have built from source code), and it does not look like any of them touch the C:\Program Files\... directory. I have all of my Engine versions (as well as the Launcher) installed on the D:\ drive on my computer, and the only related folder in my C:\Program Files\... directory is an empty “Epic Games” folder that does not appear to be used by anything. All of my projects are also created on the D:\ drive, so there is no requirement for the Launcher, the Engine, or projects to be placed on the C:\ drive.
If you are using the Binary Engine that is installed through the Launcher, you can now specify where you would like to have the Engine install (it defaults to the location where the Launcher is installed, but you can install that to any location as well).