Shadow Copies are broken on Windows Home Server. To make a long story short, see
this FAQ. It's possible that you will be able to access previous versions of your files anyway, by following the steps in
this forum post. And for more information about actually using shadow copies (including how to access a shadow copy of a deleted file), you can consult the help topics that are made available when you try to access them.
I'm not on the WHS team, I just post a lot. :)