Hey ... well if he has any important info, you will want to back that up first to external media or cloud storage ( music, documents, etc )
Then depending on the make/model of computer you would either need to use media that came with it or was created( or still yet to be created if it hasnt been created yet), or if it has a recovery partition on it use the recovery partition.
My HP that I am at now with Windows 7 64-but with Core i3 processor ( about 2 years old ) for example has a system recovery manager under Start->All Programs->Security and Protection->Recovery Manager
Depending on make/model computer it can be under a number of different paths to get there depending on where the computer manufacturer decided to place it.
If the media was never created yet for this system, I would bring over some DVD-R discs and burn a set of them. Some computers can require as many as 8 DVD-R disc's. This one required just 5 of them. Many systems have an internal counter to only allow a single set to be created, so once created these discs should be placed somewhere safe and easy to remember where they are. *Trick that I do is place them into jewel cases and then the stack of discs in cases into a ziplock bag, and then I open computer up and place the stack of discs resting on the inside bottom of the minitower and this way whenever I need the media, its right there, pop the cover off and open ziplock baggy and media is ready to go vs trying to remember what hiding place I had them so that I wouldnt lose them and they wouldnt get damaged or lost and now... they are lost.
I've lost image discs before and so I started using this method of keeping them with the systems they go with. Ziplock baggy helps keep dust out of the discs and keeps them together.
Installation clean is usually as easy as booting off Disc 1 of the set of recovery media and then following the user interface. Sometimes you have to change bios to change boot order to DVD boot first, or use boot key to be able at boot to select to boot from DVD ROM.
Newer systems also support creating bootable Flash Drives, but I personally like the DVD-R discs as for I have had USB media created that said it passed the process of making the media, but the USB Flash device didnt want to boot even when messing with bios for legacy support and more. It was an issue that the cheap USB stick was ok for storing data, but incapable of being used as a bootable device. I blew my 1 shot of making the media the counter said it was already created and I cant create another. I ended up having to pay for the recovery media for the Toshiba which was outside of warranty.
Happy Thanksgiving to you too, and anyone else who celebrates it reading this
Attachment here shows the software HP has set up for this systems recovery manager. Your friend system is probably different. They can even change between HP models.
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