I assume (Using Aol) that to carry out the software disconnect is enough. A similar option exists in IE.
My modem indicator in the task bar certainly shows no up/down activity
I also assumed that without a live connection to the internet, any anti malware and firewall software is dormant and shouldn't be reserving any memory.
I appreciate that heavyweight applications with huge files being edited do use most of what you have, but feel that if you are looking for more speed, then look first for and disable the host of things that by default tend to be present in the startup list