27" 2.8GHZ i7 '09 - laggs playing full HD .mov

[Lifequest]

Tried continuing on from a 2008 post, but I don't think anyone would be scrolling to the bottom. So started new thread.

My iMac i7 860 2.8GHZ
8GB 1033MHz RAM
512MB GPU
HD (if important not sure) - 650GB+ free.
Vendor: Intel
Product: 5 Series Chipset
Link Speed: 3 Gigabit
Negotiated Link Speed: 3 Gigabit
Description: AHCI Version 1.30 Supported

ST31000528ASQ:

Capacity: 1 TB (1,000,204,886,016 bytes)

MAC OSX 10.6.7

It can't handle a full HD playback that I've now rendered from Adobe After Effects. This is a .mov file playing on quicktime.
I tried VLC player (latest version) and it still skips frames and freezes for seconds at a time.

Activity monitor shows: CPU at 92.7% idle (though, I do see it spike down to 49.9% idle just by sitting here and doing nothing).
RAM: 1.36GB free and 4.75GB inactive
Processes: 99

I can't see why I should be lagging playing a simple 30second clip.

Could anyone help me? Or share some light on this matter?

 

[MythicFrost]

Perhaps go to apple.com/trailers and pick one and watch it at 1080p and see if you get any stutters. If not, perhaps the .mov file is corrupted or some settings are wrong?

I watch 1080p trailers from apple.com/trailers on my i7 09 model and it works fine.

 

[spacepower7]

What codec did you render it into? You need to know that in order to determine what computers can play it. Find out about it with the mediainfo app from macupdate.

 

[applegenius83]

You have 99 processes running? That's crazy! I only have around 60 on mine. You could try shutting down some unwanted trash, maybe that'll help.
Your machine is perfectly capable of running 1080p video. My 24" iMac can do fine, and your processor is about twice as fast. Your system is capable, it is probably the file. Check and see if you have a problem with any other 1080 video files. You said you've already done this, but try out a few more applications. You could also try playing the file on a different computer.
If that doesn't work I'm guessing it is a hard drive fragmenting problem. Either that or your on your way toward a hard drive failure. I've seen systems slow down a ton and then the HDD goes out. Back up your data! Grad a hard drive defragmenting app and try cleaning up your disc.
I've heard about PRAM and SMC affecting speed without affecting CPU usage, it sounds like what you have. Here's how you reset the SMC:
Shut down the computer.
Unplug the computer's power cord.
Wait fifteen seconds.
Attach the computer's power cord.
Press the power button to turn on the computer.
Also resetting PRAM: Shut down computer. Press power button. Hold Option + Command + P + R keys all at once. You will hear the chime your Mac usually sounds, and as long as you hold these keys down, your computer will keep resetting, shutting down, and chiming until you release. You should let it reset a few times and then boot normally.
Hope that helps!

 

[Lifequest]

What codec did you render it into? You need to know that in order to determine what computers can play it. Find out about it with the mediainfo app from macupdate.

I will check this.
I transferred the file over to my Macbook Air and even the Air plays 1080p smoothly.

So the file isn't corrupt. Maybe the codec is missing. Will also check out everybody else' suggestions. Thanks so much.