OS has been slow on program startup, freezes for up to 2 minutes

Question

Hey everyone,
Have fixed many PCs in my day because they broke and I haven't had much experience on Macs because they just never seem to break and I am just not start where to begin troubleshooting. I have a refurbished (from Mac) Macbook Pro which I purchase about a year ago. 2.54 Ghz core 2 duo, 4 gb ram, running OS X 10.5.8 it recently has been freezing for long periods of time while starting programs.
When I got the computer it was running great, now it lags at certain times such as program startups and waking up from sleep. The freezes can range from 30 seconds to 3 minutes of idling where I can move the mouse around but the pinwheel spins and I can hear the hard drive working. It almost seems like some memory issue as if the computer is having a hard time getting going. It reminds me of windows computers that were infected with viruses that needed to be cleaned up. Sometimes it will run okay but other times if I open a program it will stall and take a while to open, most of the times when the program is finally open it runs smoothly.
The hard drive is 232 gb. I  thought it might have been caused by space issues but when I freed up to 50 gb I still noticed the problem occurring. Right now I have 9 GB free - I know its low but I still don't believe it should be hanging for 3 minutes when I start some programs.
I am new to Macs but have troubleshooted many Windows computers and my question is where do I look from here? Is there a place that logs the computer activity during the slowdowns so that I can pinpont the issue?
Thanks for the help!
Here is a screenshot of activity monitor while copying a file over to an external hard drive that I have: http://i.imgur.com/4LXBN.png
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Screenshot of system memory: http://i.imgur.com/YYKNf.png

Answer 1

I'm not sure what you mean by "crashing" but this is what has happened to me and a bunch of other users:  When working with plugins that have visual analysis and with these plugins open Logic Pro lags very badly.  You can't stop it.  You can't make adjustments.  You just wait for the lag to catch up, which sometimes takes up to two minutes, depending on the stress you are putting on the system.  If this is the case with you as well, join the club.  It's a problem that has been well-documented on here.   It occurs for me when I open channel eq and have the visual analyzer button engaged.  As soon as I open two instances I will get this lag. 
I had a rather depressing conversation with a fellow at the top of tech support today, who still hadn't heard of this problem.  All I can say is, CALL APPLE TECH SUPPORT!!!  Make sure they know this is a problem you are having!  Otherwise it doesn't get placed into the heirarchy of bugs that need fixing.  That's exactly what I was told today and it made me very upset because I have called support, and I have seen that many other folks have done the same.  Apple is so large a company they just don't take things seriously enough to need to fix them until they receive calls.  So please, call if you can!  Ask to be put on with second tier support.