This is exactly the sort of thing Chat GPT is so good for. I just checked and asked if it's possible to keep your Windows7 laptop as a dedicated Word processor and it said:
Yes — absolutely. An old Windows 7 laptop can still be perfectly usable as a dedicated word-processing machine, especially if you deliberately keep it offline.
A good setup
Keep Windows 7 offline. Don't connect it to the internet, Wi-Fi, Bluetooth networks, or email. Windows 7 no longer receives security updates, so using it online is risky.
Install Microsoft Word if you already have a compatible version, or use a lightweight alternative such as LibreOffice (an older compatible version may be appropriate).
Store your documents locally.
Transfer finished documents using a USB stick to a newer, protected computer.
Consider disabling unnecessary startup programs and services to make the old laptop feel faster.
If the laptop has an old mechanical hard drive, replacing it with an SSD can make a surprisingly large difference.
You can make it almost like a dedicated typewriter
For maximum simplicity, you could configure it so that:
Power on → Windows → Word → start writing.
You don't need antivirus software, a web browser, email, or an internet connection if the machine genuinely stays offline.
One thing I'd recommend: don't routinely plug unknown USB sticks into the Windows 7 machine. A safer workflow is to use one dedicated USB drive and scan files on your modern computer before transferring them.
If you tell me roughly how old the laptop is (or its make/model) and whether you already have Microsoft Word, I can suggest the simplest setup to turn it into a distraction-free writing machine.