Upgrade from SL to XLion

When you upgrade from Snow leopard to X lion i paid for it via itunes where is this upgrade file stored on my imac?

Not sure what you mean. It should be in the app store and in your iTunes.

I mean the upgrade file where is it on my imac harddisk and what is the file name??

Once you have finished downloading it, it will be in your application folder, with the icon of a cd with lion on it. right after the download it will ask you if you want to continue upgrading. if you say yes, it will go thru the upgrade process. after your computer finished the upgrade the upgrade fils inside your application folder will be deleted automatic.

and also in lion you will have an extra partition called recovery, it works like the SL cd. the difference is its just a partition and to access it you need to press option button during start up.