ive purchased a laptop from a friend of a friend. he brought a newer and better one. the laptop, p4 2.8g 512RAM XP Home Ed 60g HD, i checked the manufacturer and believe that i got a pretty good deal. until i ran into this problem. once in awhile when i boot up, the hard drive (guessing) would make clicking noise. when that happens any programs that i would run would lag and ill get a unknown hard drive error. then xp would shutdown "to prevent a serious problem". I removed the hard drive to check its connector and pins. it looked fine. after i reinstalled it into its bay and booted the laptop again, it worked fine. i tested by opening all my large applications and doing everything possible and it ran smoothly. several days later, the noise would return and so did the error. so im confused and need guidance on what should i do to permanently fix this problem.