Your memory is running at 800MHz. What speed did you expect it to?
5-6-6-18 isn't great, if you set the timings in the bios to whatever the packaging says things should be quicker,
Oh, and under 32 bit you'll see no difference at all. System stability might suffer slightly. Unlikely that 8gb will do you any good even with 64 bit, as it's reasonably difficult to use up more than 4gb.