Does Icon on Desktop Slow Computer?

Let's be clear: lots of icons on the desktop have no impact on your system speed, period. It has a small impact on how long it takes to redraw the desktop, but that's very minor. What's more interesting is what a cluttered desktop often represents.

Do Desktop icons take up memory?

No. They are NOT loaded into memory. The little picture representing them which takes up almost 0 memory is, just like if you had windows explorer open and were looking at a folder with the files.

What is the purpose of My Computer icon on a desktop?

Desktop icons are designed to enable quick access to frequently-used programs, files, folders and so on. Many of these icons will be shortcuts, which are used to launch a program (or whatever) from another location.