Hi
Welcome to the HP forums! It is a great way to engage, post questions and find resolutions by working with specialists in the HP community. I understand that the computer overheats and the fan makes a loud noise.I’ll be more than happy to assist you here.
A commendable job was done by diagnosing the issue correctly before posting your question in the HP forums. It is always a great pleasure to work with tech-savvy like you. Kudos to you for that. You are a valued HP customer and we appreciate you greatly for doing business with HP. Thank you for giving us the privilege to assist you on this platform. 
For better clarity and to assist you better I would require more information regarding this.
Please provide the complete model# of the All-in-one.
For now please visit these links to for further assistance.
Link 1: http://support.hp.com/in-en/document/c03712115
Link 2: http://support.hp.com/in-en/document/c00847274
Link 3: Please visit http://hp.com/drivers and update the bios
Please run diagnostics on the HP all in one by visiting this link to ensure that the hardware is fully functional. Link: http://support.hp.com/us-en/document/c03463381 and make a note of any failure code.
Hope this helps. Let me know how this goes. I genuinely hope the issue gets resolved without hassles and the unit works great. Please reach out for any issues and I'll be there to assist you.
To simply say thanks, please click the "Thumbs Up" button to give me a Kudos to appreciate my efforts to help. If this helps, please mark this as “Accepted Solution” as it will help several others with the same issue to get it resolved without hassles.
Take care now and have a splendid week ahead.