Upgrade my old mac to Lion - already purchased for my laptop
So a while back I purchased a macbook pro and paid to upgrade to Lion. I didn't want to quite switch my 2008 iMac because I still loved using the "chat" app and didn't want it to convert to iMessage just yet. Well, now I'd like to upgrade the iMac to Lion so that I can make the switch easier when the new OS comes out this fall. Wondering how to do this? Both computers have the same apple ID but when I go into the iTunes store it shows that Lion is 19.99 still. Wondering how to upgrade the iMac for free?
iMac, Mac OS X (10.7.2)