You have to be an Administrative-level Windows user not a Standard user.
Also the software wont simply uninstall if it included Family Protection, Parental Controls or Anti-Theft.
In the case of the first two you would need the user name and password for the Administrator who set them up. If the last one it can't simply be uninstalled without a lot of security measures as it is designed to prevent theft.
Technical Support can help with that, they are available free of charge by phone or online chat and linked under Useful Links at the top of this page.
If none of those were installed and the software simply wont uninstall, maybe because of corruption, you can uninstall it using the MCPR removal tool and reboot immediately afterwards. Note that using the tool without going through the normal uninstall procedure will leave a license showing as used in the online account. If there's a subsequent problem with that then Customer Service can sort that out later on (Useful Links again).