What are the new Kernel 2.6 features?
 

I want to know whether replacing my 2.4.1.9 (I'm not quite sure if it is so...) kernel with kernel 2.6.3 will improve the performace of my system (?) and whether there are any important improvements in it (?)

In my opinion, most of the new features in the 2.6 kernel are aimed at servers running multi-processor machines. To a home user running an average desktop multimedia system you won't really notice any great improvement. But don't let me put you off. If you've got the time, you could do worse things than get more familier with the way your system works.