I am researching Windows Home Server prior to the installation of it in the coming days and I found out this little bit of info from Microsoft herself. It is contained in the Windows Home Server Technical Brief for Drive Extender at the end of the brief, also to be found as general tip in the Wikipedia entry for WHS in the section Features – Shadow Copy.

Disabling Volume ShadowCopy Services and reclaiming the disk space

1. Run mstsc.exe to start a Remote Desktop Connection session to your home server.

Caution
Be careful when using a Remote Desktop Connection to your home server. You can damage Windows Home Server functionality if you use it incorrectly.

2. Open a Command Prompt, Click Start, Run and type CMD
3. To delete all of the existing volume shadow copy snapshots and reclaim the disk space used by the snapshots, type vssadmin delete shadows /all
4. To disable the Windows Home Server storage manager service from taking future snapshots, type regedit
5. Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Home Server\Storage Manager\Volumes.
6. Find a sub key which has a MountPoint value equal to D:
7. Under that key set the value of SnapPeriod to 0

I consider this an important tip as it is not every day a company tells you not to use a feature in their software.