Here's a handy trick I discovered recently when I needed to get a lot of server serial numbers pretty quickly. Normally you have to login to the Dell or HP management website and dig around before you can get the serial number. Sometimes the website doesn't work and you're either negotiating with the local support guy to go find it for you (and then the data's suspect by definition), or you're just out of luck.
You can grab this easily from the command prompt. Look up the wmic switches for info on connecting remotely to a machine:
C:\>wmic
wmic:root\cli>systemenclosure get serialnumber
SerialNumber
ABC12345wmic:root\cli>exit
C:\>