why my macbook shows its fingered

i bought a macbook few months ago from a person was involved in clothing business and in internet marketing.i had to clean its all documents what was actually his job.Regardless i found this macbook sometimes very slow in operation ...which should not be , i have clean its ,its has faster ram as well,well now i am having trouble with this as i guess its hardware number is tracked or fingered. i am not getting proper response on my traffic pages and my sites are going down with google ranking since i started to work on it , is there any hidden tempering system inside of it thru any software or my guess is wrong for what ....?can someone answer me please .need to inform is that i use my ip usually the same for my other desktop...but the problems only shows what job i have done in macbook recently.Checked also firewall too.