you can get server specific hardware, such as motherboards which allow for multiple CPU's (redundant hardware, so that if one fails its still runnibg) and heavy duty hardware designed to take more wear and tear than an average PC would allow

I think...i know the motherboard think at least, were doing that in college
And to run a server you need a specific OS, such as Windows Server or i expect theres a linux distro designed for Servers (ill eat my hat if there isn't)