Does Sdelete Program need system rebooting or shutdown normally?

I use Sdelete from Ms Technet.

(http://technet.microsoft.com/en-us/sysinternals/bb897443.aspx)

Just one simple question,

Does Sdelete need system rebooting or normal shutdown after completing process?

The command I used is '-c'(clean free space) and '-z'(zero fill).

I mean, without rebooting or shutdown system normally, are there any problem with completing secure delete process perfectly?

(My Case : I confirmed sdelete process was 100% complete, after that the client system was shut down suddenly by blackout. I'm doubting about reliability of work. HDD(samsung) that I used was not for server system, just for normal desktop.)