I can't download songs I have purchased on iTunes

I've got two computers: a desktop running 32-bit Vista and a laptop running 64-bit Win7. I just got an iPod a couple weeks ago and I've purchased some music on iTunes using the desktop. However, I've installed iTunes on my laptop, but I can't access any music I've already purchased on the iTunes on my laptop.

I can access it fine on the desktop, but my laptop doesn't have the already purchased music available for download. I haven't bought any music using my laptop.

What I want to know is whether this can be fixed or not, and if so, how do I do it?

 

I'm using the same account on both computers. I don't get an error message and I can access the store. But, on the left side of the iTunes window, in the category "Store", underneath the button "iTunes Store" there is a button, "Purchased", that shows all the songs I have bought. This button shows up on my desktop, but it's not there on my laptop.