You don't have to get a new hard drive, just reformat the laptop, reload your OS and start fresh . Please be informed that all your data will be lost if you do reformat. You can get a windows password disk and go that way if you have data you want to recover but its faster and easier to reformat. This [https://www.lifewire.com/free-windows-password-recovery-tools-2626179|link]can help with resetting lost passwords. But unless you need info on the computer I would just reformat . Dont forget you will need the OEM key. If its not on the back of the laptop you will need to use a key recovery program [https://www.magicaljellybean.com/|like this]. To recover the key remove the hard drive connect it to another computer and run the program to recover the key. Hope this helps