Here's a nice little trick you can do on Linux, if you need to reduce CPU usage (for example, to allow a poorly cooled CPU to cool, or to save CPU cycles for something more important, like a game):

You can send a process a signal called SIGSTOP, and (unless the process is PID 1) it will stop, no questions asked. The system will still remember the process's state in RAM (though it could be swapped to disk, of course), and you can resume it by sending the process SIGCONT when you're ready for it to use CPU cycles.

How to send a signal? Well, if you know the process's PID, you can just use the kill command; the syntax is "kill -STOP $PID" to stop it, and "kill -CONT $PID" to resume. If you do not, or if there are a bunch of processes with the same name that you need to suspend (chromium is one example), you can use pkill instead: "pkill -STOP chromium" will pause all chromium processes (this will, of course, make the browser unresponsive, as it's now suspended).

Anyway, perhaps it's now time to ask the question contained in the title: Can you suspend processes in a similar way on Windows?

I usually pkill -STOP firefox before I go to bed so it won't heat my room..

Darn websites have gotten so power hungrry :(

Yes. Download Process Explorer and right-click -> Suspend. (Then right-click -> Resume). I've used this before with certain games that max out the CPU / GPU when minimized.