- With iOS 5 you can update via wifi and not loose anything unless something goes amiss.
- Since you have iOS 3.1.3 you likely have a 1G or 2G iPod. A 1G can go to 3.1.3, and a 2G to 4.2.1. Only 3G and 4G iPod can go to iOS 5.
- To identify yours:
Identifying iPod models
- If you can update do the following:
- Transfer iTunes purchases to the new computer by:
iTunes Store: Transferring purchases from your iOS device or iPod to a computer
- Transfer other music by using a third-party program like on of those discussed here:
newer copy
- Connect the iPod to the computer and make a backup by right clicking on the iPod under Devices in iTunes and select Back Up
- Restore the iPod from that backup. This will also update the iPod
Note that the iPod backup that iTunes makes does not included synced media like apps and music.