By all means, please destroy the laptop.
At the very least do not let your old employer know.
If there's personal data on that laptop, and you tell your old employer, you just made your employer aware of a data breach.
Having a data breach can have serious consequences for your employer, depending on where you live these can be fines or having to notify all the people who were affected in that data breach.
For all intents an purposes, it's best for your old employer to never know anymore about that laptop.
Come on: it's been 10 years.