Cancelling recently applied OPT

[netcoder]

Hi,

 I have completed required credits in my university in Dec and have applied for OPT. My application status still shows as under process and now I'm planning to cancel my OPT application and register for anther course with my current university. ( registration for this starts in 3rd week of Jan) 

- once I applying for cancellation of OPT will I be eligible to register for new course with the university or will I be treated as out of status. 

- how long does OPT cancellation process generally take. Will cancelling in any way affect when I apply for OPT in future. 

Please suggest.