Having a nightmare with iphone

Hi All, I'm new to this so please forgive me if this is in wrong place etc.

I'm not a very technical person and am having real problems and I hope that you will be able to help me out.

I have just purchased the new iphone 4s and would like transfer all mesages contacts etc from my old 3gs iphone to the new one. They transferred the numbers in the store and told me to back up the phone at home and then restore the new phone from the old backup on itunes. following me so far...

This is fine in principle but my old mac..running 10.4 is on its last legs to be honest and I know that the new iphone 4s will not work on it so I plugged the old 3gs into my sons pc and did an back up in his itunes. Then when I plugged the new phone in to the pc it told me that the latest version needed to be installed so I did that....then plugged the new 4s back in and tried to restore from the back up but it told me it coudn't do it.

I also backed up the old phone on my mac just to be safe..thats the one its synced to anyway.

I then updated the software on the old 3gs to the latest sofyware hoping that was why I was having the problems but now it seems to have totally reset the old 3gs....its asking to set it up as a new phone or from the backup...but when I request to restore from back up it says that the backup session has failed!!! Grr

Now I have none of my mesages on my old phone by th elooks of things although I haven't got past the start up with this and I obviously don't have them on my new phone and I really need them.

To make matters worse...since updating the software on the old 3gs it now nolonger works on my old mac as it says its running ios 5.0.1 but the old mac is running 10.4 like I said.

I take it that the backup on the pc hasn't worked properly so was wondering how I could restore the phone form my mac......please please please any ideas wold be greatly appreciated.

I'm sorry I'm not being very technical but I hope I've kinda made some sense...help please xxx

Hi there!

I'm really sorry about the delayed response.

Sadly, you need the latest version of iTunes, 10.5, which will only run on Macs running OS X 10.5 or later. How old is your mac? What kind of Mac is it? The reason why you're getting those errors while trying to restore your 3GS is because your computer cannot run the latest version of iTunes.