Unfortunately there is a forum rule which states the following.
No subject matter will be allowed whose purpose is to defeat existing copyright or security measures.
What's really unfortunate in this situation is the fact that we can't substantiate your ownership of this computer. There for I can not help you with the password. But I do have an alternate suggestion. You could use a program like Darik's Boot and Nuke to overwrite the whole HDD/SSD and then download a Windows 8 or 8.1 ISO image which you can use to create a bootable installation disc.
You can download the ISO image at Windows Eight Forums.
How to burn ISO image using Windows Burn Disk Image.
Notice: This applies only to Windows 7 and Windows 8, earlier versions do not have this.
1. Place a blank CD or DVD in the tray of your optical drive and close the tray.
2. After you have downloaded the ISO image you want to burn right click on the Start orb, then choose Windows Explorer.
3. When Explorer opens click on Downloads in the left pane. Scroll down till you find the ISO file you want and double click on it. Click on Burn Disk Image.
4. In the image below you will see Disk burner:, this should be set to the optical drive you want to use. Click on Verify disc after burning if you want to Windows to verity the disc image after burn. Click on burn.
5. In the image below you can see that the green progress bar, when the image is finished burning the bar will be filled.
6. After the image has completed being burned click on Close.
In order to do this installation you will need the product key. You can find a download for a program to find the product key and instructions for its use here
Once you have created the installation media and have the product key, follow the instructions at the Windows Eight Forums.