So you bought a used MC75 and need to reset it back to factory defaults?
Download this file:
http://2xod.com/articles/MC75/MC75_Cl...
Extract contents "Clean Boot and Blank" into a FAT formatted micro SD card.
Insert the SD Card and perform a cold boot (Press 1 + 9 + Power) and immediately hold the yellow barcode trigger button to initiate the process.