Since you are capped at 4GB of RAM, you cannot load many Kontakt libraries. Use the Freeze button on the track. It renders the track to audio temporarily, freeing up all the RAM. Unfreeze to edit MIDI later.
Let’s address the elephant in the room. Why are hundreds of people still searching for "how to install Cubase 5" every month? cubase 5
The Crack Economy. Cubase 5 was the last version of Steinberg’s flagship that had a famously stable, easily accessible crack (via a patch called "Air" or "R2R"). For a generation of producers in developing countries or teenagers with no credit cards, Cubase 5 was their first DAW. Since you are capped at 4GB of RAM,
Yes, but only under specific conditions. Yes, but only under specific conditions
Do not buy a new $2,000 laptop to run Cubase 5. That is a waste. However, if you have an old Windows 7 laptop gathering dust in a drawer, installing Cubase 5 transforms it into a professional beat-making station.
Steinberg wants you to upgrade. They will tell you that the new audio engine, the VariAudio 3, and the MixConsole are superior (they are right). But the soul of music production isn't in the bit depth; it's in the flow.
Cubase 5 offers a blazing fast, low-fatigue workflow that modern DAWs have lost in exchange for infinite features. If the limitations don't scare you, the vintage version of Cubase might be the secret weapon your studio needs.