This is an old old scam and I am really surprised that your friend has not heard of it. Easy enough to get names and addresses these days.
But that aside providing your friend did not download anything the 'Microsoft' guy asked him to or allow him access via some remote software then it looks like an unfortunate coincidence.
So we will need to know if your friend did anything the guy wanted him to do.
By the way I could go on any PC in the land and bring up a box, usually Event Manager and show you what looks like problems, most of these are no big deal but I admit can look a bit daunting, with their red/yellow triangles, to the less informed.
So if you can provide as much info as you can we might be able to get your friends PC back up and running.