Questions about HP ProDesk 400 G3 MT

Yes, myself :) You have to patch ESXi 6.0: You need the Realtek driver and the additional Sata support. Don't forget to activate the VT functions in the BIOS.

According to the product page and that there is no dedicated GPU installed, the PCIe x16 slot therefor must be free. The other question you should ask yourself, is how much the power supply delivers. According to another retailer that lists this product, it has a 180W power supply. Hardware Reference Guide: http://h10032.www1.hp.com/ctg/Manual/c04830838 Maintenance and Service Guide: http://h10032.www1.hp.com/ctg/Manual/c04887112

There are a total of 3 S-ATA connections, 2 of which are occupied. Most detailed list of specifications: http://www8.hp.com/h20195/v2/GetPDF.aspx/c04853085.pdf

I haven't checked it (because I installed windows 7 directly) but I suppose that it is Windows 10 that is installed from the start. Anyway, if a version prior to Windows 10 is installed, Microsoft will offer me a free upgrade to Windows 10.

I can't imagine that the power supply has much more power than the PC needs. But you can certainly install a power-saving graphics card (like the Gtx 750ti).

The computer has a VGA socket and a DisplayPort. With the integrated Intel HD Graphics 530, two monitors with FullHD resolution should not be a problem.

Yes - that should not be a problem... Internal drive positions 1 x 8.9 cm (3.5 inch); 1 x 6.35 cm (2.5 inch) / 8.9 cm (3.5 inch)

No, it doesn't. But you can get a USB part for a few francs.