A lot of Dell computers were sold to large companies and so forth, last time I worked for the Cooncil they had nothing else.
They had the computers set up in networks with all major programs on a separate server and the computers only had enough software to boot into the network. All data was stored on the servers so individual units only needed small disks.
Looks as if you might have to install your own operating system.
Did the seller say that an operating system was included?