Start > Settings > Control panel > Administrative tools > Computer management > Disk management.
Run chkdsk on the drive where Windows is installed:
Right click the drive in "My computer" >> Properties >> Tools >> Check now. Tick both options and click "Start":
Also - Run the System File Checker:
Click Start >> Run >> Type
sfc /scannow (note space after sfc), then click OK.
You will/may be asked to insert your Windows disc.
The file check may take a while to finish.