But why does it now show any video? when booting up?
If an OS cannot load you will not get video of any kind, are you able to get into the BIOS, do you get a BIOS splash screen when whatever the brand of notebook such as Dell or HP flashes up.
Fan is working the only time it beeps is when i plug/unplug the AC plug
Could be a battery low charge warning.
Some pointers for you;
When troubleshooting notebooks when possible I always remove the main power brick** and use only the AC adaptor to power the computer.
If the HDD has failed you should get an onscreen "no bootable device" or similar message displayed, if you are not getting this, any BIOS or splash screen then something else is wrong, in this instance I would start by removing the RAM.
Please post the brand and full model name or number of the notebook so that we can do some research.
** It is not always possible to remove the main power brick on some notebook and netbook type computers as they are sealed internally.