Strange Macbook 13" lagging issue.

Hi all.

Recently my dad put in a bigger harddrive in my macbook 13". He put the same harddrive in that he used for his 13" MBP, everything worked fine. However in my MB13" ever since the new hard drive has been put in there has been a lag issue.

What I mean by this is that the thinking symbol comes up for no reason, the computer 'freezes' for about 2 seconds then carry's on with it's business.

I downloaded something called 'hdapm' - which was meant to fix this issue but it hasn't.

I'm aware I might need to post specs and such in order to fix the problem, however I'm not that good with mac's yet so if I need to do this any help in how to do so would be appreciated.


Thanks in advance