Probably, you have junk stuffs in your computer cause slower.
Increase RAM will not help much speed. Won't notice big different speed.
I never like Intel Celeron Processor. One thing, people can afford to buy lower price like Celeron or Netbook's Intel Atom.
Celeron & Atom are slower than regular Intel P4 or Duo Core.
Best way to wipe out your junk stuff - re-format/re-install OS.
Most time, I do reformat HDD then re-install everything.
