I’m not convinced PeppermintOS is the ideal “beginner” distro as LXDE is missing some of the GUI tools for achieving certain tasks … having to manually edit /etc/samba/smb.conf to share a folder springs to mind, not a show stopper for a slightly more advanced user, but you get my point. (FYI, it’s as simple as a right-click in Ubuntu, similar to Windows)
Nor as a “showcase” distro … people coming from the Windows world are (IMHO) more likely to notice Peppermints perceived shortcomings when directly compared to Windows instead of its strengths.
Ubuntu on the other hand is both an ideal “beginner” and “showcase” distro … works “out of the box”, yet with plenty of GUI tools to help get it the way you like, it will allow people to experiment, yet with good support if things get out of hand, and it’s an ideal platform that allows people to slowly get used to Linux without actually NEEDING the command line.
Don’t get me wrong, PeppermintOS is a great little distro, and certainly my current favorite … but then I no longer consider myself a “beginner” and would probably have found it a little harder to begin with than Ubuntu … I started with Ubuntu, and I’m glad I did, indeed I still use it on my main PC.
… though yes I NOW prefer Peppermint.
IMHO, Ubuntu first, then switch to another distro if/when you feel more at home, and/or feel the need.
Actually, I tell a lie … my first experience of Linux was Redhat 4, which is why I immediately went back to Windows
… Linux was somewhat harder to transition to back then 
Ubuntu was the distro that grabbed me and held me 
@BkS
Are you now recommending distributions that you haven’t tried yet ? 
and answer me this question … which distribution was it that helped you learn, and got you hooked ? … I’m betting it was Ubuntu 
I’d also suggest there may be something wrong with your setup if Ubuntu is “slow” on your system … it runs perfectly happily on my Pentium 4 (dual core) with 2GB RAM … so should be even quicker on a Core 2 Duo.
OK it’s not a “speed demon”, but it’s still reasonably nippy.
Didn’t we have to partition your HDD because of bad sectors … could it be that rearing its head again ?