I wanted to pass on some information that might help some people.
CS2 Media Cache Files were stored in the project folder that you created to save your project.
ALL CS4 Media Cache Files are saved on the c drive under c:\your name\documents\adobe\after effects cs4\media cache files
I found this out the hard way when I was trying to instal the After Effects 9.0.1 update and it told me I was out of Disk space. So I freaked out and did some investigating and found the media cache folder on my C:drive utilizing over 30 gigs of space. So I moved it over to another drive.
There is a check box in preferences that lets you keep them next to original when possible but it is not as tidy as the old way.