How safe can I overclock my HD 7750 on a 300w?

i wouldn't do it. that psu is small as it is... maybe spent a few $$ to get a little bigger psu? and if it does run that great why overclock and have the chance to fry your card? just because you can?  

You didn't mention your other components, but you should be fine. The 7750 only uses 43w, you should have no problem maxing out Catalyst Control Center manual overclocking.

There's no huge danger if you don't adjust to voltage. Crank the core and memory clock up in Catalyst Control Center and run graphical benchmarks or games and see if it's stable. I haven't messed with any 7750 but I have OC'd a few 7770s and with two of them I was able to get 30% overclocks with minor voltage bumps and the other one got away with a 15% overclock but it was stable at those clocks on stock voltage. Tinker and have fun, read a guide if you're not sure what you're doing. Tiny voltage increases are okay, just don't get too crazy with it. Try a program like MSI Afterburner it will give you a little more control.

This shouldn't be answered without first having asked for full specs on the power supply (on the sticker on the side) We need to take our time and do this right, not just rush to answer.

While the additional power draw on the PSU is probably minor, it wouldn't recommend it at all if it is, say, a store bought HP.

If you want to overclock safely, get a larger 400-450 watt power supply. Not worth OCing on a 300 watt power supply IMO.

Dave

I respectfully disagree. 300watts is more than enough. His GPU draws about 45w on load. Overclocking it with 50 millivolts added on (he wont even need that much) is not going to shoot it up into the 100w range. He can overclock, and probably reach the GPUs clock limits with no damage to and without reaching the power limits of the PSU. I feel this is a non-issue. His card could never draw more than 75w from the motherboard, there are no PCIe 6/8pin connectors, and the card was designed to use much less than what a PCIe slot can provide.

I don't like the fact that he has 300w PSU. And it probably is an OEM that either came with a budget case, or from an OEM computer. His PSU could pose a problem to his system in the future but it will have nothing to do with an overclock on the GPU in question.