weird lag FFXIFollow

like everyother battle, at somepoint in the fight ill get R0 and about 10 secs later ill come out of it. but its really annoying. and if im on for more than a few hrs the S will drop to about 25 making the game really slow. can someone please tell me whats going on.


cpu specs----------

intel pentium 4 proccesor
speed: 3GHz
total hard drize space:229 gigs
free space:142 gigs
ram: 502mb
graphics card: ATI radeon 9200