How do I get my itunes back on my computer if the drive crashed?

Answer 1

Install a new hard drive
Reinstall operating system (assume windows)
Reinstall itunes (get from www.apple.com)
On iTunes deauthorize all other computers, then reauthorize this one again.
Plug in your iPod. For your purchased music, iTunes will suck those out of the iPod. For music you didn't purchase, I hope you had a backup.