I've just ordered a WD passport HDD thingy to match my MacBook Pro 
I'd like to keep my iTunes on there, so I can also maybe play it on my PC.
How would I do this? Do I need to just drag iTunes to it and tell iTunes on both machines where it is? Will it keep saving new purchases on there as well?
Thanks in advance.

I'd like to keep my iTunes on there, so I can also maybe play it on my PC.
How would I do this? Do I need to just drag iTunes to it and tell iTunes on both machines where it is? Will it keep saving new purchases on there as well?
Thanks in advance.