The ram you bought will work, but... Where it's non-ecc there isn't any error correcting as gheist mentioned, and the reason you got the message about it being slower is that it is as it has a higher clock latency than the original ram. If this is just a test or non-critical server using non-ecc ram will be fine but if its a critical server then i'd spend the money and get ecc ram. Also just to note you don't want to mix ecc and non ecc ram in the same system.
