Physical memory on my laptop?

The system already handles that for you through the process of paging (swapping). Older versions of Windows were less pro-active in their paging efforts but still way better than randomly killing processes.

Finally, determining which process to kill would also be a small challenge on its own since it's not possible to know if you use a program actively if it's not the active window.

To emphasize how much I think this is a bad idea, even though I could do it in less than an hour, I wouldn't even give it for any amount without a written agreement freeing me from any liability.

Here we go again with the use of the word Memory.

I assume you are referring to RAM (another conflicting name)

Only programs you have asked to run will be in RAM so as you say uneeded programs will not affect RAM usage.

If you mean data stored on the Hard disc there are programs around that will monitor program usage. Google it.

The Anti virus program Avast attempts to do that.

The safest way is for you to look at all your programs/apps and decide yourself.

How about a reboot.

is your hard drive check in computer