Multiple itune libraries

Sorry I've search but still confused.
Anyway just before Xmas I had a blue screen death on my iMac so after a quick search,
I decided to reinstall snow leopard.
Now after the install I went to sync my iPhone 2 and iTunes came up with "this phone is synced with another library do you wish to replace......."
Well since then the hard drive killed it's self so I replaced it with a terabyte and reinstalled.
Tried to sync iTunes and got the same thing, so does that mean that I have 3 libraries?
And if so what do I do now as I can't sync my iPhone as I'll stuff things up.
Please help.

If your library on your newly installed iMac has ALL the songs/videos/apps/whatever you want to have on your iPhone then you can safely ask it to sync with the new library so that it will erase everything on the iPhone and sync everything back.

If, on the other hand, you have stuff on the iPhone that doesn't exist on the iMac, you want to save that first before you do the sync otherwise you'll lose it and have to remember what it is so that you can download them again..

So tell us a little bit more about what your library on the iMac has and what if anything is different on the iPhone and we can suggest the best step forward..