If you can rebuild a laptop with an external CD Rom drive?

I have a workforce who has a problem with their laptop and that can't be fixed anymore. That's why I want to rebuild the laptop for him, and reinstall Windows 7. The laptop did not seem to have a CD Rom drive. My question is now, does anyone of you know if I can rebuild the laptop with an external CD Rom drive? I'm just not so sure about that, I mean, these things have to be installed by the system and it is no longer possible to log in. Would be glad if someone could give me an answer.

Starting with an external CD drive should work, but you may need to adjust the boot prio.
As an alternative, you can also take a USB stick, but should have a certain speed so that the installation works fine.

Yes, that usually works. Possibly. Must be pulled in the BIOS / UEFI the drive in front of the hard drive (in the boot order) or just once in the boot menu to be selected. On too old computers, however, it may not be supported by the BIOS to boot external USB CD / DVD drives, but if it was originally Win7 on it, it will probably be new enough.

Just boot from the installation CD on the external drive. If booting from CD works, then you can also set up the computer without any problems.

Normally, there's always a function to reinstall even such computers. Maybe there's even a recovery function that you only need to call with a shortcut. Then there's a hidden partition on the machine, which is then called.