I'm guessing that you are trying to run too many programs with too little RAM, and the operating system is needing to swap the contents of RAM to the hard disk every time you switch applications. This is a sign of a very bad memory setup that will also cripple your performance within After Effects.
What are your Memory & Multiprocessor settings?
See
this page for information about memory and performance in After Effects.
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Todd Kopriva, Adobe Systems Incorporated
Technical Support for professional video software
After Effects Help & Support
Premiere Pro Help & Support
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