Straz, welcome to the Forums!
The problem is, some programmers use these standard folders hard-coded in their software. I used to do this as well - I would think "I hate these stupid names, let me delete them"! I would go ahead, delete them and then next Windows update does something to the Media player and voila - My Music is back where it was.
As a result, I simply ignore these folders, don't use them at all. I turn them off in my start menu and I store my actual files on a whole other hard drive - not the one where Windows is. Therefore on another hard drive - but it could be another partition or even the same old C:\, although I would recommend separating the OS and your personal files in case you'd need a re-install - you could create any storage scheme you want with whatever names you want.
So the bottom line is - it's possible to delete them, but it's very probable they will re-appear, or even give you an error - for example if a program wants to access them, but does not have enough privileges to create them. Thus the simplest solution is to ignore them.