Ugggghhhh! Tried upgrading my Dell Dimension 8100 from 128 MB to 1Gb (2x512 cards) Got the cards, put them in, got 3 long beeps, no monitor screen and 2 orange lights (instead of green) under my keyboard plug in. Oh, now my old memory doesn't work either. After this happened, looked at the cards and realized they shipped ECC cards for my non-ECC motherboard. I hear that ECC can work with non-ECC but, obviously, it didn't work in my case. Should I exchange for the non-ECC cards? Did I know just enough about computers to zap mine? I'm at a loss right now. Please advise.