Error Message:

Convert cannot gain exclusive access to the file system drive, so it cannot convert it now. Would you like to schedule it to be converted the next time the system restarts (Y/N)? drive letter

Explanation:

A user or system process is using the specified drive. User processes are processes executed by running applications. System processes are processes from volumes with active paging files. An active paging file cannot be locked.

User Action:

Stop other running applications and try the conversion again. Or, type Y and Convert will schedule the volume to be converted the next time the system restarts.