RESOLVED : Acer 4740 running very slowly on Ubuntu Lucid lynx
This problem can occur because the memory priority is set to optimize the Virtual Memory. So your Virtual Memory (Swap) will be very busy than your Physical memory (RAM).
The Virtual memory had a huge difference with Physical memory (RAM is more faster than the Virtual Memory), so your Computer will be slow down drastically.
This Problem can be solved by changing the memory usage priority to RAM, not using Swap / Virtual Memory. you can follow this step to change the Ubuntu Memory priority :