500Watt PSU enough for GTX 275

Plug your system specs into this and let it 'do the math" for you:

http://www.antec.outervision.com/

That card pulls 123 watts

I tried a similar PSU calculator, and the result is that i would be fine with 380 watt PSU. But i also read somewhere that for the GTX 275, you should make sure that 12V1 give 20A, and 12V2 gives also 20A. But on the sticker on the PSU i see only 1 value for 12V, giving 20A. Maybe this is a problem? And even if i try it anyways, i cant harm the other components if something goes wrong and PSU cant take the load?

A good 500 watt power supply is enough. A no-name generic probably won't be.

First, A high quality 500 to 550 watt psu will have a +12 volt rail rated at 40 amps. The current (amps) on the +12 volt rail of your generic power supply is low. At only 20 amps the maximum wattage for the +12 volt rail is 20 amps x 12 volts = 240 watts maximum. Your going to come up short while playing games.

Second, the power supply should be at least 80+ Bronze certified for energy efficiency. There are some models available which have achieved 80+ Silver and 80+ Gold Certification. In all probability your power supply is not energy efficient. It will run hotter and deteriorate quicker.

Third, the official Nvidia recommendation is for a system with one GTX 275 video card is a 550 watt or greater power supply with two, 75 watt, 6 pin, PCI-e power connectors.

My best advice is you should consider getting a new power supply capable of delivering the necessary power to your system.\

Corsair and Seasonic are two of the brands that have a reputation for high quality power supplies that consistently earn high marks in technical reviews. They are reliable, stable, and come with a 5 year warranty. Some of the newer models come with a 7 year warranty. Lately we've been seeing a few other brands offering some high quality units. One example would be the Antec Earthwatts series which is a major improvement over Antec’s older psu’s like the Basiq models.