Why does my iTunes library disappear when I switch the computer off?

[MmeLindt]

It is driving me crazy. I am able to restore it as it is all still on my iPhone but I can't be doing this every day.

Any changes that I made yesterday are gone too. I made a playlist for DH's birthday party and it is no longer there.

Oh, and I am getting this message "your iPhone can only be synched with one iTunes library. Do you want to replace all data on your iPhone with this library?"

I had to set iTunes up again after I bought a new computer, but how can I have two libraries. And if I do, how do I find out where it is and cancel one of them?

You can have more than one library - I remember researching it when I was trying to work out how to synch DH's iPhone on a pc with a load of DD's crap music on - you are supposed to be able to create a new library if you hold down shift while opening iTunes. It never seemed to work for us, so we ended up just creating a new folder for DH & only syncing that one - but could you have created a new library by mistake & now be trying to sync with the wrong one?

Thanks, Rusty. I think that is what I must have done. 3 computers in about 6 months, I am confused.

Got it sorted, I was synching with the old iTunes library so the new one was getting deleted.

I have lost two audio books though, annoying as I had not finished listening to one of them.