As you might know Microsoft decided not to have Clean Disk enabled by default in Server 2008 (R2) for whatever reason but I still like to use it to delete unused files… at least on my private server.
If you could enabled a feature called Desktop Experience to enable Clean Disk but that would also give you Media Player, Themes and other programs you would not wanted on a server but here is a way to get Clean Disk without doing that on Server 2008 R2 64-bit.
Browse to this folder and copy cleanmgr.exe to your Windows\System32 folder
You also have to browse to this folder and copy Cleanmgr.exe.mui to you Windows\System32 folder
Now you can click start > run and type in Cleanmgr.exe to start Clean Disk in Server 2008
You can also click start and just type Cleanmgr in the search bar.
Further info about this and folder location for other versions of Server 2008 and Server 2008 R2 you can find here.