How do I find the serial number of my Macbook Pro in Windows 7?

Use the following command in windows command prompt tool

wmic bios get serialnumber

I don't think you can get the serial number from Windows. I recommend getting the S/N close to a bright light and writing down the S/N as best you can. You can use this site: https://selfsolve.apple.com/agreementWarrantyDynamic.do?sn=730300257XJ to verify the serial number is correct. It will show you the Ghz which you can verify by going to System Properties (right click on My Computer and select properties)