I have a 350 rosewill in my current computer, should I try with that one?
Try it, it won't hurt. Unplug unecessary devices and just see if it gives power. If any fans or lights come on, then its PSU. If not, then I would take a further look into the mobo and try that PSU in your old system.
Well I don't have a multimeter, so I think I'll just RMA it. Few questions though, the psu came with the case, do I have to take out everything and rma the case aswell? And how to I go about doing a RMA?
Try some different memory too - I had issues with my Gigabyte 965P-DS4 board, which were attributed to the memory being incompatible. The system wouldn't boot at all with some OCZ memory, so I tried some Kingston ValueRAM and it worked perfectly... I'm still RMA-ing the board due to other issues anyway tho
Maybe stupid questions but does the power supply have a black toggle switch on the back where the power goes in? Do you have the leads from the front panel switch on the right pins on the mobo for it to power on with the case switch? And, before you RMA it would it be possible to take the supply out of the case and try it on the system you got the known good supply from? if the possible bad supply does not work on a known good system then it is most certainly bad.