Who is referring to DOS in Windows 7? Let's be more clear on what it is taking place here. There is no DOS in Windows 7 as it ceased to be used in Windows XP. The command line option to preform commands that looked like DOS were performed through a completely different file. DOS used command.com and NT systems use cmd.exe to execute commands and batch files.

Disk checking is vital to the health of the PC and to the ongoing health of the hard drive. As far as hard drives not failing as often these days I'm not in agreement as I see them daily in the overall workplace of small businesses and residences. Hard drives old and new are failing regularly. Sometimes it's due to negligence such as overloading the hard drive with data (more than 80% full) and not regularly defragmenting them. Auslogics has one of the best defragementers that also optimizes the hard drive. So regular treatment, hard disk checking, cleaning (CCleaner), and defragmenting/optimizing are highly necessary. I personally advise weekly such disk treatment and the time to do so becomes minimal due to continual application.