You need to learn how to save to the mmc (that is, one of the SD cards that goes in a slot). It's not a matter of what you have open. (It's like a hard drive problem, not a RAM problem.) You can move stuff out of the device memory by using File Manager (in Utilities menu of App Mgr).

Also, please click on both the Newbie links in my signature, below. The second one is, in form, tongue-and-cheek, but the info is sincere. And see this post, too.