RAM woes. HELP!!

[Arun the Gr8]

My bios shows that the latency of my DDR memory is 2.5; what does it mean? WhatI

mean is how much is optimal. Also I am planning to buy 2 1 GB DDR RAM chips from a

company called US Modular because they are cheap. They are available for $26 each

(my uncle will be bringing them for me from US) as compared to $53 for Kingston for

each such module. I need the memory only for an year or 2 since after that I will

get a new PC.
What I wanted to know is may I buy them or shall I buy Kingston?

Also what is ECC or Non-ECC memory? What difference do they have?

The last thing I wanted to know is whether RAMs having different latencies but same

frequency work together?

[Choto Cheeta]

All Memory (Ram) related queries here.