MacBook (late 2008) is really slow

Question

Hi folks,
so here's the situation. My gf's late 2008 MacBook ist annoyingly slow. I have 8 tabs open in Safari and when going back and forth between those tabs it gives me the spinning beachball for like 30 seconds. Sometimes it even reloads the whole tab which takes even more time. The whole time I hear the hdd working hard, it's clicking all the time though there are no unsual sounds that would indicate harddrive failure.
I checked disk utility it says S.M.A.R.T. is verified. I even used another program (don't remember the name right now) to get a more detailed description of the hdd status, progam says everything's fine.
I checked the memory both with the tools provided by Apple and memtest, both say everything is great.
So I asked some Apple Service person what the problem might be, he said if SMART's okay than it's probably the hdd-cable - repair would cost me (or my girlfriend in this case) 60 bucks. Before I shell out the cash I want to double check and see if I can repair the computer myself. My plan is to connect the hdd via usb to see if it's still that slow, but of course the speed of usb itself is limited, so I'm not sure if this is a good idea.
btw. the MacBook is running OS X Lion, has 2GB of RAM. And I repaired permissions, took me couple of hours but it's fixed now.
Thanks for the help

Answer 1

Okay, I forgot two important things:
The MacBook was already slow before I upgraded it to Lion. I hoped an update from SL to Lion would fix the problems but it didn't (didn't make it worse though)
The MB once fell of the couch. After that the display backlighting behaved strange, when closing the lid it would switch on again (determined by the illuminated logo) for a couple of seconds than turn off again - this happened while the rest of the computer was on its way to sleep mode. Funny thing is this strange behaviour was fixed after I upgraded to Lion (and I have no clue why, because to me this sounds like a hardware problem).