Dell Inspiron 1545 -- Full Recovery E: Folder - Help

My Recovery E: Folder is full -- 31.9MB free of 14.6GB - Windows Vista. I keep getting pop ups/messages saying that my E: folder is almost full, and occasionally that I should close my internet browser so I don't lose information. 

I've checked out other forums and discussions about how to fix this problem but none have worked so far. Some of them said to go into the E: folder and delete files which should be there (can't access it the folder -- there's only a warning message) or to change the Drive Letter (get a message that says it cannot remove "the letter drive of your volume", and now I'm not sure what I should do next. Help??