Nope you cannot remove them. I suggest watching this to learn more about the upgrades. Edoreld's tutorials are great.
youtube.com/watch?v=IuSDUq001Ss
Edit: That's better. I had to remove the http:// to get it to stop trying to show it in the thread.
In the latest version, picking up the machine retains the upgrades, so they can't be removed at all.You can remove them, but only by taking up the machine and putting it down again. AFAIK there's no other way of doing it, though you do get the upgrades back.