I wanted to provide you few solutions but I have stopped myself as that can corrupt your computer system:
Anyways you can try this basic step if you know when the issue begin. It's known as system restore
Click on start, all programs, accesories, system tools and then system restore. in the sys restore window click on next and then from the calender select a bold date on which system was working fine. Keep clicking on next and continue. It will restart the system. Check the issue once you are back to widnows.
System restore will not delete any data but will do any software chnage you have made to the system.
If the issue is not resolved then you can try creating a different user account.
The steps are:
Click on start and then control panel. Click user accounts. Then pick a task. Create a new account. Name it and then make it Computer admin from account type drop down box. Click create an account.
Close the windows. Click start, log off, swithch users and then click on new account. Once in try thge ext hdd.