Songs I bought won't transfer... please help!

Question

Firstly, I am a techno-dunce and tend to avoid forums as I never understand the language used in the answers to my questions... so please help me but keep it veeeeery simple!
My Ipod was registered to 2 computers in Ireland, where I was living, and I bought tunes on one of the computers from the Irish Itunes store.  Everything was synched to my Ipod... so far so good.
When I left Ireland I did not have any of my CDs so was advised to use something available free on the internet, xilisoft?, to get the music onto my computer, which I did, putting an Itunes library on my new coputer with all my music in it, including the songs that I had bought online.
I am now living in Australia, and my Ipod is registered to my new laptop.  (I had no idea there was a limit to number of computers you could register an Ipod to, and now have no access to the old computers to deregister them.)  I have bought a few things through Itunes library over the past couple of years and wanted to make sure everything in my library was in my Ipod so I synched it last week.... and got a message to say that more than 40 tunes cannot be transferred to my Ipod as they are not authorised to be played on this computer!  It seems that the tunes I bought on the Irish computers will not transfer but the ones I bought on my brother's computer in the UK 2 years ago, have transferred fine.  I am baffled as to why there should be any difference between those bought in Ireland, Uk, or Australia, since they were all bought on my account in my Itunes library.
I am pretty ****** off as I paid for them in the understanding I would have them for keeps, not realsiing that Itunes may decide I actually can't have ethem, after all!
Because I have zero technical knowledge, I have no idea what to do about it.  I would really appreciate any help you can offer, but as I said, please keep the language and instructions extremely simple...!!!!!
Thanksps I don't know what kind of Ipod it is, I am guessing it is the classic, it's about 6 years old and doesn't do anything fancy like the newfangled touchy ones. I am using an Acer laptop with Windows, if that has any bearing on anything!

Answer 1

I have a similar problem, although not exactly the same. I downloaded two full albums. For each album, there is one song that cannot be copied to my iPod (tried w/ 1GB Nano and with an older Shuffle). In fact, every time I try to copy these songs to an iPod, I hang up not just iTunes, but my entire OS 10.3.9 system. A reboot is required to end the hang and get back to normal.
These songs are on my computer. They play properly. The only thing is that I cannot copy them to my iPod. Any ideas why not? (All the other songs from the same albums copy without any problem.)
G4 400 Mac OS X (10.3.9) USB 1.1