How can I listen to the music/songs or watch the movies in my iTunes library if I've damaged/lost my iPod and use a system-reovered/new computer?

Question

I accidentally dropped my iPod Classic 160 GB into the toilet
bowl of my home sometime ago, and unfortunately enough,
as misfortunes seldom come singly, I got a serious problem
with my computer ( an HP Desktop) and had to do the system
recovery which, as you know, removes everything in the system
drive. After having reinstalled iTunes, I thought I should be able
to listen to the music I kept in the Library of iTunes, but I don't
see any of my music/songs or movies there. Thus come my
three questions below:
1) How can I locate and enjoy the music or movies I saved in
the iTunes Library with a computer after its system recovery
or even a new computer?
2) Like the current situation I'm in, when my iPod is damaged
or lost, can I still enjoy the music or movies saved in the
iTunes Library from my computer ( meaning without an iPod)
if I have the iTunes application installed in it? How? Do I have
to sign in my account? Sign in with my e-mail address saved
in my account? Where can I find the sign-in webpage of iTunes?
(Please provide me with the related link of the webpage.)
3) The above issue brings up another question, are the music/songs
and movies as well as other programs in the iTunes Library saved
in my computer or in Apple's server?
Please, with your kind patience, let me know as detailed as possible.
And also let me know what Apple's e-mail address I can use to ask
for support on such issues as described above? Although I always
prefer asking for support or help by e-mail, I would also appreciate
if you could let me know the phone number I can use to ask for
such help.
Best regards,
Lawrence Wood

Answer 1

System Recovery generally assumes you have backed up your data somewhere first. If not, you're in trouble.
Depending on your region you can recover most of your previous iTunes purchases. Install iTunes. Use Store > Authorize This Computer... and Store > Sign In... then select iTunes Store in the left-hand column and click Purchased in the Quick Links section on the right. You should now be looking at a list of past purchases that you can download to your computer.
See also: HT2519 - Downloading past purchases from the App Store, iBookstore, and iTunes Store
Your purchase history is preserved on Apple's servers. Anything you ripped from CD or downloaded from elsewhere was stored on your computer and should have been backed up.
There is no live telephone support for iTunes issues. For problems with a particular purchase contact the iTunes Store support staff through the report a problem links in your account history, or via Contact Support. For general issues with usage this is the place to get help.
tt2