I just bought myself a second pair of matched DDR DIMMS for my PC now that I've upgraded to Windows 7. Thankfully they cost less that £10 on ebay. I say thankfully as one of them is faulty. So which will give me better performance? 1) 1.5 GB PC4400 DDR in single channel mode. (2 x 512MB original + 1 x 512MB new) 2) 1GB PC4400 DDR in dual channel mode. (2 x 512MB original) EDIT This may be academic as I'm getting blue screens with the 1st option. I might just have to bin both new sticks and write it off as £10 down the drain.