Was this a prank call or a scam (see details)?

After getting onto my computer, I noticed that it was acting slowly. This is not that unusual when I first get on, though it did seem a little worse than usual. I then got a phone call saying that Microsoft noticed that my computer was acting slowly and asked to press 1 to speak to a representative. This seemed odd, but I decided that there could not be any harm in pressing 1. After pressing 1, there then followed someone saying good-bye and then hung up. I figure it was probably all fairly harmles, but am curious as to just what was going on. It may just be a coincidence, but the computer started working at normal speed right after the phone call.