Ipod

 If you purchased your songs from itunes, then install itunes in your machine, and authorize it with the itunes store. Unfortunately without 3rd party software you will have to do a hard reset on your ipod and reinstall itunes. Hope this helps

Straight from Mac website:

Learn how to restore iPod, iPod mini, and iPod nano to factory settings.

If you need to restore an iPod shuffle, click here.

It is important to understand the difference between "update" and "restore". Update simply installs the software that controls iPod and does not affect the songs and files stored on iPod's disk. Restore erases the iPod's disk and restores iPod to its original factory condition.

Warning: because Restore erases all of the songs and files on iPod, make sure to back up any files you've saved on the iPod disk. All of your songs, videos, podcasts, audiobooks, and games can be loaded back to your iPod provided that you have them stored in your iTunes Library. If you use the Nike + iPod Sport Kit, see this document for more information.

1. Ensure that you have an active Internet connection as new versions of iTunes and iPod Software may need to be downloaded to your computer.
2. Download and install iTunes 7.0 or later if you do not already have it installed.
3. Open iTunes, and then connect your iPod to your computer using the USB or FireWire cable that came with your iPod.
4. After a few moments, your iPod will appear in the Source pane in iTunes.
5. Select your iPod in the Source pane and you will see information about your iPod appear in the Summary tab of the main iTunes windows.
6. Click the Restore button. You will be prompted with one or more restore options that may prompt iTunes to automatically download the latest iPod Software. The 4 possible restore options are:
7. • Restore Option 1: Restore - Restores with same iPod Software version already on iPod.
   • Restore Option 2: Use Same Version - Restores with same iPod Software version already on iPod even though a newer version is available.
   • Restore Option 3: Use Newest Version - Restores with the latest iPod Software available.
   • Restore Option 4: Restore and Update - Restores with the latest iPod Software available.
8. If you are using a Mac, a message will appear prompting you to enter an administrator’s name and password.
9. A progress bar will appear on the computer screen indicating that the first stage of the restore process has started. When this stage is completed, iTunes will present one of two messages on screen with instructions specific to the iPod model you are restoring.
10. • Restore Instruction 1: Disconnect iPod and connect it to iPod Power Adapter (typically applies to older iPod models).
    • Restore Instruction 2: Leave iPod connected to computer to complete restore (typically applies newer iPod models).
11. During the stage 2 of the restore process, the iPod will show an Apple logo as well as a progress bar at the bottom of the display. It is critical that the iPod remains connected to the computer or iPod Power adapter during this stage. Note: The progress bar may be difficult to see since the backlight on the iPod display may be off.
12. After stage 2 of the restore process is complete and the iPod is connected to the computer, the iTunes Setup Assistant window will appear asking you to name your iPod and choose your syncing preferences similar to when you connected your iPod for the first time.

If you don't have iTunes, go download it for free here: http://www.apple.com/itunes/download/

Then open iTunes and plug your iPod into you new computer. You will be asked if you want to reset it and sync it with your new computer's iTunes library. Put your music in iTunes and it will sync.

Nooooo!!!!!!! No need to do that!!!!!!! If you still have your music in your ipod you can fill a new itunes library with it!!! Just download copytrans http://www.copytrans.net

And do a backup to itunes of your ipod. IT will import all your songs, videos, podcasts, tv shows, ratings, playlists, play counts, etc... If I were you, I would even perform a full backup of my ipod just in case something like this happens again.

You may try this ipod transfer, it's a nice iTunes alternative that can help you manage iPod files including delete, upload, play, copy, etc. It's much easier to use than iTunes. It can also help you manage multiple iPods on one computer or manage iPod on multiple computers, even copy music and video from iPod back to computer or iTunes. So you will not lose your iPod files even though you switch to a new iTunes library. My friends recommend it to me, it works pretty well. Hope it helps. Contact me if you have any other question.

I'm using blaze ipod converter suite, it can convert any DVD, VCD, video, audio, image files into iPod, and it convert very quickly, you can download and try it for free: http://www.blazevideo.com/ipod-converter-suite/