You create partitions before the format on a new drive, if used you need to delete the partition first.
When you boot the W7 dvd choose custom install, go to disk tools, create partition, select how big you want the first partition and create, then allocate the remaing space for your second partition, you can choose to format now and continue the instalation.
how create partion of a drive at the time of formate
At the time of installation you are prompted with the question of which drive and partition you would like to install Windows 7. At that same prompt you can specify how many partitions and the size for each partition you desire.
Should you have any questions, please feel free to ask.