Type the following command on CMD window:
C:\>wmic bios get serialnumber
Result:
Serial Number
GHFLY1
To get more details:
C:\>wmic csproduct get vendor, name, identifyingnumber
Result:
Identifying Number Name Vendor
GHFLY1 PowerEdge 7050 Dell Inc.
Find My Express Service Code:
Having your Express Service Code available when calling Dell saves you time on the phone, so we offer the tools below to help you find it quickly and easily.
http://www.dell.com/support/troubleshooting/us/en/19/Expressservice