I've been using VirtuaWin to set up four virtual desktops on my computer. This makes it easy to group applications: one desktop for client T, one desktop for client I, one desktop for client O, and one desktop for other stuff, such as drawing. The most memory use I've seen on this system so far is less than 6 GB (out of 8 GB), so running virtual desktops doesn't make the performance of my other apps worse.
Using virtual desktops helps me keep things organized, but I also want to be able to quickly switch to Emacs and take notes without caring about which desktop I'm on. Fortunately, VirtuaWin makes it easy to set up an application to run on all desktops. Left-clicking on the VirtuaWin icon in my status bar lets me set my Emacs window as "Always Show". To make it even easier to consistently get to Emacs, I pinned the program to the task bar (right-click on the task bar icon and pin the program), moved the pinned program to the first slot on the task bar, and got into the habit of using Windows+1 to switch to the application. Yay!
VirtuaWin is a free open source program for Microsoft Windows.