Itunes backup problem

[SgtSmackSmith]

Hey I a iPhone 4 running 4.2.1 and I want to update it to iOS 5. The problem is that I haven't synced this phone in almost year and the computer that I did back it up on has all my iTunes stuff (music, apps, backups, etc.) but iTunes won't start and I can't reinstall or uninstall, so I copied it all to a new computer but now my only choice is to update and lose everything or restore from a year old backup. Neither are a choice because I have added many important contacts and need my current text messages. Is there anyway to just backup my phone to a new computer that has the exact same files as my old computer that it was synced with before?
Thanks

 

[bab2010]

It's simple.
1.) update iTunes
2.) connect your iPhone to your computer open up iTunes and perform a backup of your iPhone.
3.) upgrade your iPhone iOS to the latest available one.
4.) after the iOS upgrade is done, connect your phone to your computer and open up iTunes and restore your backup to your iPhone.