Multi Desktop from PDF-Convert, Inc. is a handy tool that helps you run more programs and open more windows without getting the screen too crowded.
When a lot of windows are open on the current desktop and you run out of work space, you can switch to another desktop, which appears blank, and continue working there. Your windows on the first desktop stay as they were, so you can return to them at any time.
The current version is 3.00 and runs on all Windows versions.
Good to know: Windows 10 and Windows 11 also include built-in virtual desktops through Task View (Windows key + Ctrl + D creates a new desktop), so check whether the built-in feature already covers your needs.