plugged nano into friend's comp. how to fix it?

when I first got my nano, all the songs already on my
media player were transfered to my iTunes and ipod,
which I didn't want, and then I took it to my
friend's house and plugged it into her computer
thinking I could download my own songs onto my ipod.
When I unplugged it some of her songs replaced all of
the other ones I had on their. Not even all of her
songs were put on my nano, and I really don't like
the music she listens to. So I took it back home and
when I plugged it in and clicked on "Selena's iPod"
(my name) the playlist was dim, I couldn't click on
anything, take songs off, and I can't even add my own
songs onto my iPod now. I don't know what to do, my
friends have tried to help me, some say I need to
restart it but I don't know how and my "iPod Updater"
file is empty. When I tried using the Help section on
iTunes or the iPod website, I didn't see any icons or
tables or any of that stuff that they were talking
about. Someone please help me because I've had this
expensive iPod for a month and haven't even been able
to use it thank you

DELL