...I don't remember exactly which buttons I pressed in sdminst, but SD card was not inserted on some operations (for the clear reasons, I do not wish to repeat it now). After computer reboot, OS was not started. Using boot CD with disk editor I have seen that first partition of my HDD was 2MB FAT16 and second partition was FAT32 with invalid size. Using recovery software (commercial) I successfully restored old partitions layout (NTFS+extended).
The same was reported in the german forum, a guy killed his boot drive this way, another one an USB pen...
A very good OS recovery software for such things is "TestDisk" from
http://www.cgsecurity.org/wiki/TestDisk !
When the Windows drive letter changes / the SD card is removed & inserted again, the drive selection in sdminste.exe changes to an other drive letter, e.g. the hard disc drive.
So when you use sdminste, ALWAYS look to the "Selected SD card drive" combo box BEFOR you press ANY button !