If you're running Windows 7 and its the first partition, then it's probably the System Reserved partition. Win 7 created it and puts the boot files there. Look in Disk Management - right-click the Computer in the start menu and select Manage to see Computer Management, which contains Disk Management. The partition should be called System Reserved and include System and Active as attributes (hover over the partition to see all the attributes).
If it is System Reserved, don't try to delete it. Your system won't boot anymore. The best thing is not to worry about it. If you really don't like it and aren't comfortable fixing up unbootable systems, then you would need to install Win 7 again, either to a partition created with Vista or using Diskpart (search for "Windows 7 100mb partition diskpart" without quotes and you should find how to use it).