Whenever I launch a program (or something starts automatically) or unlock my screen, my laptop lags for about 1-2 secs. It's not too much of a big deal, but it can be annoying especially when watching a video or looking at a website. When I listen to the hard disk it seems to sleep and wake itself frequently.

My computer: Dell Studio 1535, 3gb of ram, Intel® Core™2 Duo CPU T5800 @ 2.00GHz × 2 75 Gb filesystem size, Ubuntu 12.10 32 bit.

Any suggestion would be appreciated . Thanks in advanced.