If you need a defragger use free Puran from Puran Defrag Download
It has the valuable feature of running a defrag with full Disk Check in Boot mode so that file system is checked and System files can be defragged which are not reached from the OS. It also has an Intelligent optimizer option selected on the Additional Operations tab which improves disk performance.
First test your HD SMART status with CrystalDiskInfo - Software.
Then before doing the Boot Defrag with Disk Check, run CCleaner - PC Optimization and Cleaning - Free Download
both Run Cleaner button, and Registry tab with back-up selected.
THis will test the HD, clean and optimize it perfectly.
In addition work through these other Troubleshooting Steps for Windows 7
to see if the failure was logged, google it or any repeat errors text and ID to resolve them, establish a Clean Boot, use System Resources to check for problems. If you stay within those steps you will learn the troubleshooting and optimizing fundamentals and cause no problems.