Dell Precision M6600 :: Randomly Freezing - System Often Recovers After Several Minutes

System: Windows 7 Professional 64-bit Service pack 1

Problem: The laptop freezes several times a day, since we got the laptop two years ago. The freezes occur without dependance on how much hardware resources is the system using - it can freeze during video compilation or just when reading an internet article. The freeze is typically several minutes long, then the system often recovers and does all the events tasked to it during the freeze at once. When it doesnt recover in ten minutes, I turn the laptop off/on. Then all the files which were being written during the freeze have correct file size but are full of zeroes.

During the freeze itself, either it freezes when the light of HDD access is off - then sound doesnt work and mouse cursor is frozen too, or when the light of HDD access is on - and the light keeps shining during the whole freeze (not just blinking as usual), mouse cursor can be moved (but has Busy icon) and sound plays. It is possible to alt-tab into another window, but its not possible to use applications, run another application, or get to Start-menu. When you try to use the application you alt-tab into, it just goes non responsive until the freeze ends, then everything you inputed is performed at once.