I'm guessing your 2007 macbook is running Tiger (10.4.x), as that is what it came with. Since then there has been Leopard (10.5.x), Snow Leopard (10.6.x), and the newest Lion (10.7.x). Take note that there is a difference between upDATE, and upGRADE. An update is free within each version. So if you are running Tiger, you should have 10.4.11, which was the last official update for that version. Read all about it in http://support.apple.com/kb/DL172
. On the other hand, an upgrade is a completely new operating system, and is bought. In theory, all of them can run on your macbook, however ....
I'm also guessing you've got only 1gb of ram. Because each newer version needed more resources, you'd need more ram to upgrade. Leopard will run better with 2gb. Snow Leopard and Lion are OK with 4gb. So you'd want to add if you upgrade.
Lastly, Pandora is supposed
to run on Tiger, based on specs. Try updating first, then check out if it will run.