I can also recommend OpenShot Video Editor. It's quite simple to use, and it's free.

It runs on Windows, Linux, Mac.

I used it for creating a video from pictures and added background sound.

You can also add additional timelines , i. e.:
one for still images,
one for videos,
another for backgrund sound,

and then rearrange them simply by dragging around at the timeline. You have a choice of several blending funktions, and you can export in many different formats.

How it works: https://www.openshot.org/videos/

Because it's freeware you also find a lot of tutorials at youtube.

If you not rely on a windows OS, like staciejaxx said, you can give Linux definately a try.

Linux, same as with Mac OS (because both were developed from UNIX) are not threatened by windows viruses and trojans.

But Linux is for free, while Mac OS is quite expensive.

On Linux you get all standard software like
firefox browser,
thunderbird eMail-client
libre-office writer(word), calc(excel), impress(powerpoint)
vlc media player
GIMP image manipulation
Gajim xmpp chat client with OMEMO
and thousands others.
There is kind a appstore included with most Linux distributions

Which Linux?
Debian is great and very stable. https://www.debian.org/distrib/

Ubuntu uses the debian repositories, but you will get new program versions sooner as with Debian stable (but there is also Debian unstable with new codes)
https://en.wikipedia.org/wiki/Ubuntu_(operating_system)
https://www.ubuntu.com/

There are variants of Ubuntu with a different style, but more important: also different systems requirements.
Lowest is Lubuntu, wich is also very similar to windows 7. This will run on your old laptop.
You have a taskbar on the bottom, program-starter at the left down corner, and even the windows-keyboard-shortcuts will work like
win + d minimize all windows
win + e open file explorer
and so on: http://www.comfsm.fm/~dleeling/tech/lubuntu-lxde-openbox-desktop-keyboard-shortcuts.html

For your old Laptop you should try Lubuntu, thats Ubuntu with a lightweight Desktop (LXDE)
https://lubuntu.net/
https://en.wikipedia.org/wiki/Lubuntu
I am using Lubuntu for years now. It's on this 8 years old computer I am using right now. I do all my internet and office work with it and never had problems.
After startup, the taskmanager showes typically a system usage of 1%, RAM is used 250MB of 4GB.

You can download the iso for free (like all Linux systems) at https://lubuntu.net/
Then install it with unetbootin https://unetbootin.github.io/
on a flashdrive and start it on your laptop or almost any other PC-hardware.

You can also install and try multiple Linux-iso's on one flashdrive, using the windows-program Multiboot: https://www.pendrivelinux.com/yumi-multiboot-usb-creator/

Important: not all hardware is supported by the different Linux-distributions.
You can simply check your old laptop by starting one of the Linux-iso's. Just try it, you cant break anything.
Or check at google (searchterm: your laptopmodel + linux / ubuntu)
and https://www.linuxjournal.com/supportedhardware
and https://wiki.debian.org/Hardware

If you want to buy a newer laptop, I would recommend a windows 7, up to 5 years old, and the make a dual-boot with Lubuntu. Thats what I am doing for years now. You still have windows if you need it, but for daily work there is Lubuntu.