Currently I have a Single monitor Desktop system. And I need an another Monitor. I have one Loptop.
How to use that Laptop as my 2nd Monitor?
You can give Synergy a try… it’s for sharing a single keyboard and mouse across two PCs running windows. You need to set up one of the machines as Server the other will then attempt to connect to it. This implies that you also have a WI-FI router.
p.s: the software is open-source, hence free, although they currently heavily rely on the 1$ premium version of the program with added functionality.
Hope this helps.