Meaning those few hours you won't be able to use that PC when your friend remote in. Your friend remote in from external thru the internet or locally thru local LAN?

If thru internet, the answer would be Teamviewer or Anydesk. They are free.

If thru local LAN, Remote Desktop Connection (Windows feature).

You can read more about Anydesk and Teamviewer free and paid version difference on the official website. That's the easiest way. But there are more complicated way with more secure, not recommended for non-IT profession.

Under normal situation, we won't allow anyone to remote our work or personal computer. People can hijack your files or info. If you keep personal photos or videos in the computer, I won't be surprising to see another case of some nude photos or dirty email/chat leaking on internet. And I won't be surprise if your Lowyat forum account, bank transaction & login info, email, social media account got hacked.

Anything they wanna do, they can do on their own computer. Why must do on yours? If he remote your computer and do some hanky pranky thing such as hacking, spreading malware, then you are the one to be get caught and charge.