The option to withdraw from a course through ISIS ended on April 4, 2014.
According to PRP 3462 Undergraduate Course Withdrawal Policy:
No withdrawals will be permitted after the end of the tenth week of the semester.
Prior to the last week of classes, in exceptional circumstances, for compelling, justified and documented reasons, the Dean of the College in which the course is being taught may waive these restrictions. Poor academic performance will not constitute grounds for late withdrawal. Please see the Office of the Registrar regarding this policy.
If you wish to withdraw from the university completely you have until Monday, May 5 to go to the Office of the Registrar and fill out the University/Term Withdrawal form.