Clipbox is a free, open-source clipboard utility for Windows. It holds text you copied (writes to disk). It is a very simple tool, with minimal resource usage.
The advantage of writing to disk is that you can recover copied data even if your computer hangs or crashes. It works with only does plain text. In its window, the clipboard entries can be viewed and recovered.
It is portable software and does not require installation. It does not add any entries to your registry either.