Hello Uzhan,
Welcome to the HP Forums, I hope you enjoy your experience! To help you get the most out of the HP Forums I would like to direct your attention to the HP Forums Guide First Time Here? Learn How to Post and More.
I understand that your getting a error that your fan is not working on bootup and your system is failing the memory tests. The issues you are describing both appear to be a physical issue and I think it would be best if you contacted HP technical support for repair options.
US support link to contact options for HP products purchased in the US.
Outside of US support link to contact options for HP products purchased outside the US.
If you are out of warranty and wish to work on this yourself I would be happy to assist you, but first I would encourage you to post your product number for your computer. I am linking an HP Support document below that will show you how to find your product number. As well, if you could indicate which operating system you are using. And whether your operating system is 32-bit or 64-bit as with this and the product number we can provide you with accurate information.
How Do I Find My Model Number or Product Number?
Which Windows operating system am I running?
Is the Windows Version on My Computer 32-bit or 64-bit?
Please re-post with the requested information and I would be happy to provide you with assistance. Thank you for posting on the HP Forums. Have a great day!