I have an iPhone 4 and thinking of buying my sister an iPad. My itunes library/program is located on my PC.

Is it possible to some how sync my itunes account and library between my PC and laptop so both have exactly the same purchases?

My sister can use my itunes account to buy stuff from itunes. If she purchases something for her iPad, will it also sync to my iPhone? I dont want her iPad stuff on my iPhone.

So what im thinking of hopefully achieving is this; both the iPhone and iPad can connect to either the PC or laptop at any time for updates and file transfers using the same itunes account. Hoping its better to share the account instead of using 2 accounts which could mean hassle with setting up multiple libraries if thats how it works.

Nope - iTunes doesn't give you the ability to export music of devices onto computers. You would have to manually copy the music files off the PC and onto the laptop. Then you would need to ensure that the music files were exactly the same on both computers all the time - bit of a pain in the butt.

What I would do is have your main PC set up to sync but have the other one set up to so you can manually add items to it via itunes if you like.

Opps.. meant to add that if you bought all your music of the iTunes store you can actually add it to another computer using the Transfer Purchases option in iTunes

You can use iTunes network sharing option that let's you import one library from a local network PC into another library on one of your other PCs. I used this to unify my PC and laptop libraries. I had mixed results as some things didn't copy and album artwork got screwed up but most did.

Anyway I can now pick from the same library for my iPhone and iPad.

It is possible to transfer stuff and share between different computers on your network if they have the same itunes account using Home Sharing. http://theappleblog.com/2009/09/11/i...-home-sharing/

But each device can only physically be linked to one iTunes library for syncing. But after that it's easy enough to share and transfer the content between other computers on the same network.

Even if it wasn't bought of iTunes... such as ripped MP3s?

Yep or imported CDs etc. etc. The whole library can be shared.

Nice one... and can you set shared librarys up so that if you add an MP3 on one computer the other one will automatically have it also?

It's only automatic with iTunes purchases. But for anything else just click 'Import'.