Hi, I am an Independent Advisor.
Let me help you with this concern.
I understand that your machine will no longer power on and you need to wipe out the harddrive so you can have it disposed of.
If the non-functioning Lenovo C50 doesn't power on at all, it might be challenging to access its hard drive directly through another computer.
You can manually remove the hard drive from the non-working Lenovo C50. Usually, in all-in-one PCs, this could involve some disassembly. Once the hard drive is removed, you can connect it to a working PC using a SATA-to-USB adapter or an external hard drive enclosure. Then, you can access and wipe the drive using the working PC. If you are not comfortable in removing the hard drive yourself, consider seeking professional assistance.