Helping people with computers... one answer at a time.
"Volume in use" when trying to format most commonly means you're trying to format and erase the entire disk that has Windows on it.
The most common scenario for this is that the operating system itself is using the drive. For example you can't FORMAT C: if Windows itself resides on or is using C:. The only way to format a drive in use by the system is to reboot, usually from floppy, so the system isn't running. Be careful - this usually means you are wiping out your system - I'm assuming that's what you want.