If you check this page you can identify which specific Macbook you have:
That's probably the best place to start ( & you can post what you have) so either myself or someone else in the community can help you.
You should also update your profile with your Macbook info, etc... just for a future problem solving reference; that's where helpful peeps here in The Apple Support Community look to try & help you solve your problem.
I guess the bottom line that we are looking for is:
Can your MacBook support an upgrade to Mac OS X Snow Leopard (10.6) and then upgrade that to (OS X 10.6.8)? For only then can your MacBook support an iTunes upgrade to iTunes 11.1.3.
Sorry about the confusion
Snow Leopard came on a DVD when I bought it & I believe that Snow Leopard DVDs can still be puchased (new) but can your MacBook year/model/build support that?
You can get Snow Leopard here -> http://store.apple.com/us/product/MC573/mac-os-x-106-snow-leopard
- Mac computer with an Intel processor
- 5 GB free hard drive space
- 1 GB RAM
- DVD drive for installation
See the Apple up in the upper left corner. Click on that & come down one menu item to "About This Mac" & up pops the info on yer GB of RAM. If you click on the 'More Info..." button on that same window, then you'll see 'Hardware' listed with a little white triangle right next to it.
You can click on that & it'll point sideways or downwards... then if you select memory it will give you all the technical info about said RAM.
But if you want to know how many GBs of available disc space you have; then go to your Utilities folder in your Applications folder and open Activity Monitor. Click on "Disk Usage" and you'll see Space free. No not outerspace, silly, but it really is free or let's just say it's "available" as Chris mentioned.
So there you go, myragirl...