Items that have this flag are generally malware such as viruses, trojans, hijackers, spyware but could also be programs that are not desirable to run on your computer.
This is known to be dangerous in almost all cases.
How to remove 2ndThought.CF
Removing 2ndThought.CF manually is hard. You never know how many files it has infected.
Please use anti-virus to check all yours files. More details in How to Remove a Virus section.