Most comprehensive Mac testing app out there?

My macbook pro (a1150 series) has started to act out of line and just when i think that I have it figured, the odd behavior starts giving symptoms of another problems. I.E- slow computer behavior indicates bad HD but then it acts more like it didn't have enough ram. So... I want to test the machine from top to bottom. What app does that?

Incase someone wants to take a crack at it, these are the main things that happen...

Macbook Pro (1.1)
OSX 10.5.6
C2D 2ghz
2 gigs ram
80gig drive (10 gigs free)
(problems occur with or with out the computer being plugged in)

problem 1.
photoshop takes forever on rendering. I haven't put FCP on yet cause i think the render times will be dreadful. I haven't tried to capture from my camcorder yet

Problem 2.
Wireless downloads are erratic in their speeds. 900kb/sec then down to 10. This is with torrents that my imac stays steady at.

problem 3.
hard drive seems sluggish.

SO, I THINK THAT the HD is on it's way out but it could be a messy library? I have used YASU to clear things out with no avail. Guesses?

Thanks!