If you get a Check Point login screen before the normal Windows login, that means Full Disk Encryption is installed.
If that's the case, I'm afraid without having access to the Endpoint Management used to generate the installation package, there's nothing you can do to disable the Endpoint short of completely reformatting the computer.
Even if you knew the credentials to get past the pre-boot login, you need the uninstall password in order to remove the Endpoint software from the PC.
In short, without involving the previous employer, there's not a lot you can do to regain access to the existing Windows installation.