A home server desktop that can also serve as a desktop computer?

I am looking for a Desktop which is a server and has the capability to run standard OS such as windows, linux, etc at different instances. I also would like for this uber box to have the ability for multiple laptops to connect with it via wireless with limited capability to back log your data and access to specified folders. Server access would require you to log directly into the box as a server, but also this can be also used as a standard desktop with $ROOT name being the administrator and $USER names only access to desktop.