1. The 1st digit of ESN number is also 1st digit of SN
   
2. Open up calculator in Microsoft Windows
   
3. Click on VIEW at top of calculator and select SCIENTIFIC (or PROGRAMMING in Vista or Win 7
   
4. Click on HEX button at top left of calculator
   
5. Input the 2nd, 3rd and 4th characters or numbers of the ESN number
   
6. Click on DEC button at top left of calculator
   
7. These are the last 4 digits of the SN number
   

Example: ESN 26DA4A would be SN 21754