Try removing the battery and running just on AC power. Your battery may be swollen and not allowing the trackpad to click. If that's the case you need to replace it ASAP.
As for the folks telling you that you can get and run Mavericks, I stand by my statement that Mavericks is no longer available. You can't buy it, you can't download it...it's not available.
Here's the link to buy Lion http://store.apple.com/us/product/D6106Z/A/os-x-lion
Here's the link to but Mountain Lion http://store.apple.com/us/product/D6377Z/A/os-x-mountain-lion
Now if one of you will provide a link as to where I can get Mavericks I would be eternally grateful.