Asus R2h Help!!!

Hi i have just got today the ASUS R2H and it is runing a bit slowy and the wifi sum time's says limited or no connectivity and the wifi signal stength is all ways very low and on the windows task manager says the CPU Usage is at 100% a lot of the time wen i am not doing anything on it i am runing XP and i have the on with 768MB ram on it also how do you up upgrade the ram and the Hard drive? plezs any HELP!! be good thanks!!