Can't sync after installing vista

Question

My PC was recently crippled by some serious viruses and i was forced to completely reinstall windows. As i thought i was resigned to losing most of my saved items i decided that this was a good oppertunity to try out vista. However, later when i had installed Itunes and logged in with my account i reaslised that i could not sync my ipod touch with it, recieving the same message you recieve when you try to sync an ipod with another computer(it will wipe the ipod if you continue to sync). I was really hoping i would be able to sync so that i could put my music collection back onto my computer as well as my collection of applications which have cost me a considerable amount of money. I want to put them on my computer so that if anything happens to my ipod i wont lose my entire collection.
I am very new to this whole thing so i am sorry if this question has already been answered or if i have posted it in the wrong place but any help would be much appreciated.

Answer 1

Did you create or update your computer's backup for all important data on your computer's hard drive before reformatting your hard drive to install SL which should include your iTunes library?
The sync process for iTunes content and for transferring photos from your computer is a one way transfer process only - from your computer to your iPhone except for 3rd party apps or music/video purchased with your iPhone which is transferred to your iTunes library on your computer the first time you sync your iPhone with iTunes after doing so.
Assuming you didn't include your iTunes library with your computer's backup, iTunes includes an option to transfer iTunes content that was purchased/downloaded from the iTunes store from an iPhone or iPod, but this is for iTunes content that was purchased/downloaded from the iTunes store only.
First you need to re-authorize your Mac with your iTunes account with iTunes if you haven't already done so. With your iPhone connected and without syncing, at the iTunes menu bar go to File and select Transfer Purchases From - the name of your iPhone.
If all 3rd party apps do not transfer, you can re-download an app with iTunes on your computer and you won't be charged again for a purchased app as long as you use the same iTunes account to re-download the app that was used to purchase the app originally.
If you use the Address Book and iCal and you didn't backup your Address Book contacts and iCal calendars/calendar events, before syncing contacts and calendar events with the AB and iCal, enter one unique contact in the AB and one unique calendar event in iCal. Make these up if needed, which can be deleted later. This will provide a merge prompt when syncing with the AB and iCal with the first sync, which you want to select.