That looks like a rarely used processor power supply and in particular a Pentium 4, these have been used on brand name computer system boards such as HP etc, while technically as being 12V it could be connected to a GPU there are a couple of reasons why it shouldn't be, the PSUs are normally non standard ATX type and will have only the two cables coming from the PSU and both need to connect to the MB, one for the CPU and one for the mainboard power supply and the said PSUs normally only have a low to very low power output and most certainly not enough to power a gaming capable add on GPU.Will this connector work with a graphics card?
I have an Hp Pavilion 590-p0050
Sorry but the guidance is as in my reply #9, you presently have a functional computer but not for long if you start connecting things in any other way than they are intended to be, you could take out the whole computer.Would it kill my psu if I tried a 6-pin card?
Honest answer is that I would not risk using an add on video card with that PSU, the brand is bad, the output information label is badly lacking in detail, if you check the information on the PSU database here you will note that your PSU is not even listed, there is no warranty period for any of the Acbel PSUs and that most of the Acbel 300W PSUs could only actually produce 228W which is terrible.