Windows 7 PC's do not have a key stored in the BIOS. There may be an OEM SLIC table, but that does not have a key stored in it. It only has an OEM identifier. Windows 8 and Windows 10 use OEM embedded keys but Windows 7 doesn't. Factory Windows 7 OEM installs activate against the BIOS SLIC table. The key used is a generic key. Even if you know what it is, it can't be used with stock install media. Those keys are blocked from online activation. They only work with the custom branded OEM install media, and if you have that media, you don't need to know what the key is anyway. It's entered automatically. They are referred to as OEM-SLP keys. The key you use with stock install media is the key on the COA sticker. It's referred to as an OEM-COA key. That key is unique to that PC. You'll likely have to do a phone activation with the OEM-COA key. I always have the first time I used one.