So I'm a total nube to after effects and i'm running under XP on my iMac to add insult to injury ;-) but when I render my movie in the render quence it says that it is only using 12 or 13 per cent of my RAM. Does this matter, and if it does how do I fix it? Thanks in advance

Why do you think / believe this is a problem? If it needs more memory it will
probably take it. It seems it just doesn't need any more memory to complete
the task you've given it.

as rob stated, there may not be anything necessarily wrong.

however, running a virtual pc environment on an imac alone will eat a good chunk of your ram, let alone running after effects on top of it. you might experience better memory usage and performance on your computer in a mac-native version of after effects.

if you want to play around in preferences, there is a "memory & cache" panel with options you can tweak. "maximum memory usage" is the general amount of memory after effects is allowed to use (can be higher than 100% with virtual memory -- default is 120%), and "maximum ram cache" is primarily to adjust the length of your ram previews. i find the default values are usually fine, and setting these values too high will actually reduce performance by taxing your system.

Henry, he might not be running it in a virtual environment, I assumed he was
running it directly on the hardware (through Apple Boot Camp).

Thanks for the quick reply's. I am running bootcamp so that should be ok, I guess it just dosen't need all that ram. cool

Probably that for your AE composition, RAM isn't the bottleneck, CPU is.