This is NOT official HP Cutomer Support. This is a peer-to-peer user supported forum for HP consumer class products. HP maintains no official presence on this forum. It is unlikely that HP will respond in an official capacity. Any reply from a HP employee represents their own opinion and not that of HP's.
From your TigerDirect link;
Startup Operating System = Windows 7 Professional 64-Bit
Optional Operating System = Windows 8 Professional 64-Bit
Please see HP Business Support Center - Get help from HP to contact HP with your support questions.
The HP Pro 3500 Microtower Computer is a business class computer and as such, your questions may be better answered in the HP Business Support Forum.
Please click the white KUDOS star to show your appreciation