I use this, it can free up several Mb of RAM safely, protect anything you dont want to stop, (Vital ones are auto protected) then "End it all"."EndItAll lets you terminate all non-essential programs for the purpose of installing new software, running finicky games, or writing to CD-Rs that need a big buffer. The essential system programs Explorer and Systray cannot be terminated. EndItAll's main window presents a list of running processes. You can protect any process in the list from termination."
To re-instate what you switched off, reboot. Voila! back to normal
I recommend using this just for Online games and other extremely memory aggressive games.
http://www.ccs.org/Tips/Download/3Download.htm then download enditall.zip. Not tried the other apps.