Well, with all that done, i was able to notice what was causing it. I turned on a missing tab about write bytes on the task manager under "Processes", the biggest writes come from firefox. It can write a few gigabytes\day if i have a reasonable amount of tabs opened.
Now that i got 16gb of ram i hope the number of writes caused by the windows PageFile diminishes because previously i was able to fill my 4gb of ram pretty easly!
Now my last question is: how much TB of data can an intel 320 120GB withstand until it fails?
I did my search and i got mixed results, some claim that it is 15TB and others claim that it can go as higher as 600TB. Which one is more close to the truth i'll leave for you to awnser