crimsonforce :
I ordered a 400W GPU, and later found out I only have a 280W power supply. If I were to get a new power supply with 500 watts available, would it still fit in my Optiplex 745 small form factor computer or would it be too big to fit?
sorry to say it is a proprietary power supply, so you cannot upgrade it
it does have a pcie x16 slot though
so something like a 750 ti should work as long as it is a version that runs only on the power of the slot.
(no additional pcie cable power required to be plugged in)