I Get pretty bad FPS and the screen shakes i run a PC with the bare minimum requirements what settings should i use for melee.
AMD Sempron processor 3400+ 2.0 GHZ
Direct X 9.0c
Nvidia GeForce 6100
Minimum settings are just for running the games at all, not for fullspeed (no PC can get fullspeed in all games) Try setting watchdog to 15 or frame skip.
Sorry... Semprons are single-core, a GeForce 6100 won't push enough GFX power, and you never mentioned OS/RAM (although I'll bet it's Windows XP with 512MB or 1GB of RAM)
That kind of 5-year-old system will never run Wii or even GC games at a decent speed.