Giving any advice without knowing the cause is somewhat pointless.
So we need much more information from you:
1. Post the output of the following commands:
2. What machine are you running Ubuntu on, give hardware specs please. Do you have it installed natively, is it running in a virtual machine or do you run it from a Live-CD/-USB?
3. Which part exactly is slow, graphics output, disk access, launching programs, ... . Be as exact as you can.