When i start my laptop it shows on the screen Boot device not found , please install an operating system on your hard disk Hard Disk (3F0) When i go to hard drive check test it says No hard drive installed. Please check that the power and data cables are connected properly .... What should i do now
Sounds like the hard drive has failed and will need to be replaced. If you are still in warranty HP will replace it. If not a retail 2.5" laptop SATA hard drive can be used. Just be sure to get one of at least equal capacity as the original in order to use HP Recovery Media to install Windows. It can be larger, but not smaller capacity.For instance if you have a 500GB hdd you could use a 750GB hdd but not a 320GB hdd.
It might be a good idea to first check the hdd and be sure it is plugged in securely. In some instances they can lose a good connection- while jostling during transporting,etc
If you need more help selecting/replacing the hdd post back with full Model & Product Number as listed on the Servic Tag: