430watt power supply running a msi hd4850

Rosewill isn't that great of a brand, stick with something like Corsair PCPower & Cooling, FSP, SeaSonic, stuff like that. Well on the AMD page it says it needs a 450W PSU, I know thats probably more than needed, but its with a quality PSU. Rosewill isn't a quality PSU.

It's kind of hit and miss with Rosewill power supplies. A lot depends on which manufacturer made a particular model for Rosewill. JonnyGuru.com did technical reviews of three Rosewill models that actually turned out to be adequate. Unfortunately none of the reviews were for the model you purchased.

A single 4850 video card uses about 110 watts and 9 amps at full load so you should be okay.

Id be voting NO on this one.
Sure it can run everything, but a psu can also take everything down if it dies.

I replaced my 750w unit for a better quality 850w. Even though 750w was much more than i needed i found the new PSU handled voltage drops under load much better and i could actually lower the cpu voltage. The psu also runs cooler and quieter.

I needed a new psu for another system anyway, so i just took the opportunity to upgrade my own.

mrmez - Any psu, even a very high quality psu, can go bad and fry the rest of the components. Three years ago I experienced the blue ray of death when I plugged in and turned on a high quality psu. It wasn't very bright in the room so I had a good look when the blue rays shot out from the psu. Scared the living daylights out of me. At my age it's a wonder I didn't have a heart attack.

update, running solid so far, stress tested it over night and the rails stayed solid. tested with an mm and the voltages are EXTREMELY stable and im only pulling about 296 watts at full load.