Beachballing and extreme GUI latency with low CPU usage

I generally only have two applications open. iTunes 11 playing MP3s of about 128kbps, and latest Google Chrome with up to 4-5 tabs. Usually I have gmail open, Facebook, and maybe 1-2 sites such as YouTube or Slashdot. I don't have any servers running.

The CPU load is usually 90% idle. The system load hovers around 1.5 for some reason. Though at times it jumps up to 3.5 even though CPU remains at 90% idle. I read a ton of Facebook pages. After about 30-40 page loads, Chrome stops letting me scroll. I can still click in the address bar, so I know the whole system isn't frozen. I can change tasks via ALT-TAB, however, when I do that, it takes 10 seconds for it to switch to Terminal. When Termianl is finally shown, it jumps to 90% CPU for a few seconds, and updates 5 times in a row, quickly, like a stuttering video, and then it is normal. If I activate Expose by moving the mouse to the bottom left corner, it shows the Dock right away, but then it just sits there frozen for 15 seconds, and then it shows the windows and whatnot. If I switch to the Finder and click on an icon, it doesn't do anything. I then click on another icon. Nothing. I then try to draw a bounding square on the empty desktop. Nothing. Then after about 30 seconds of being frozen, the system does EVERYTHING I did in a quick hurry. It selects the first icon, the second, draws a square, selects another icon.. etc. It seems to be queueing all my actions but not responding to them immediately. If I try to delete a file, the beachball shows up, and then after about 30 seconds it shows a progress bar, even for a tiny little text file, the progress bar takes 5 seconds, and then it removes it from the desktop. If I press Mac-T to open a new tab in Chrome, I get a beachball and it takes up to a full minute before the new tab shows up!

While all of this is happening I've been monitoring my system with top, the CPU keeps at 90% idle! And the load is usually below 2.0! I have a Core 2 Duo 2.1 gHz MacBook 13" with 2GB of RAM, and there's about 25 GB free on the main disk. There is also an external firewire drive connected. Every 5 minutes the Mac OS wakes up the drive from sleep even though I'm not using it, and while the drive is starting up the whole system freezes for 5-10 seconds again!!

What the **** kinda joke of an operating system is this?!?!!? I thought Macs were multitasking and everything! I'm seriously concerned.... I"ve never had these problems in Windows, and never had these problems in Linux. ***?!!!?! I can't use more than 5 tabs in Chrome either. It's way too slow. And most videos on YouTube I can't watch unless I lower to 340p or 240p, otherwise they freeze and stuff. Even though I have enough bandwdith.. The system can't handle the video. It's so frustrating. Oh and one more thing. While scrolling through pages on Facebook, iTunes pauses at random points as if it can't handle the scrolling.... ***??!?!?!

Please help me!!! 😟