.NET developer Travis Illig is stating that a in-place upgrade for PerfectDisk doesn’t work for Windows Home Server:

PerfectDisk has a feature to "check for updates" from within the Windows Home Server console. It’s OK to use the "check for updates" feature to see if there’s an update, but do not install the update from there.

First, trying that will fail because the Windows Home Server console is open (Catch-22, eh?). Second, if you try to do the update from Windows Home Server via Terminal Services, it doesn’t quite do what you expect. I think the engine gets updated, but the console add-in doesn’t or something. Stuff gets messed up. Just don’t do it.

Travis shows us the proper sequence of events to install an update to PerfectDisk for WHS for a problem free upgrade.

You can read it here.