It looks like Todo is organization software,
I agree that your best solution would be to use the recovery partition to return the operating system to the condition it came out of the box. By doing this you will deleted any programs which were installed from a disc or download. It will remove any personal data left on the hdd by the original owner. If there is an infection this will remove it.
If you don't do this you will need to remove any programs which you don't want manually. You will need to run scans to determine if the computer is infected or not. You will need to run a program like AdwCleaner to remove any unwanted toolbars and other trash which may have been installed from a download embedded with third party software which it isn't declined will automatically install itself. You will need to run scans like sfc /scannow and chkdsk /r to determine the condition of the operating system files and the hdd. There are other things which probably should be done, but I believe you get the point.