Please Note the following , feel free to get in touch for any clarifications.

Brand: HP
Model: 800 G2
Form Factor : SFF (Small Form Factor)
Product Reference:

https://support.hp.com/au-en/document/c04802690

http://h10032.www1.hp.com/ctg/Manual/c04832374.pdf


Comes with Case+Mother Board+Heat Sink and Fan+DVD RW
OS License : Win10 Pro 64 Bit Built in to BIOS , You can install and activate over Internet. You will need OS install Disk.
Options when Purchasing :
You will need to install your own 
1. Processor (Takes any 6th Gen desktop Processor I3 i5 i7 )
2. Hard Disk /SSD
3. RAM DDR4 - Options available to purchase with RAM 4GB/8GB/16GB/32GB (Takes maximum of 64 GB RAM 4X16GB)

Comes with 1X Free SATA cable and 1X Free SATA Power Connector to plug in 1X 2.5" or 3.5" Hard Disk/SSD, You can connect additional SSD/Hard Disk with additional SATA Cable
You will also need power cord , Keyboard, Mouse and Monitor