Why is my laptop’s RAM usage so high at 90% without any apps open?

Unfortunately, without the ability to upgrade your RAM, there's not much you can do to reduce the usage drastically. A good start would be to clean up any unnecessary software on your laptop and disable any startup items that you don't need. That might ease some of the strain on your memory until you can afford an upgrade.

It's tough with 4GB of RAM these days, especially on Windows 10 or 11. If you can't upgrade, maybe consider switching to a lighter operating system like Linux Mint or Ubuntu. Just make sure you do some research first to see if it fits your needs. It might help alleviate some of the RAM pressure.

Sounds like your operating system might be using a lot of RAM up front, especially with modern OS versions. Have you checked your Task Manager for any background processes that could be using the RAM? Sometimes, there are apps running at startup that can hog resources. Also, if you have an empty RAM slot, it’s worth considering a RAM upgrade, but be sure it's compatible with your laptop. If not, switching to lighter applications can help too.