Yes. Since I think it is not possible to upgrade directly from version 6 to 10 (why not 11?) I think you mean to do a fresh install of Fedora over the Fedora 6 partition. You can do it the same way you installed Fedora 6: insert the installation disk and when you arrive at the point to decide the partition scheme of your system, choose "custom setup" and leave the Windows partition untouched. You can edit the Linux partition by simply reassigning the mount point and choosing to format them again.
If you have a /home partition and you want to preserve existing data, don't format it. Just reassign the /home mount point. In any case do a backup of your data (on both Windows and Linux). This should be a common practice and maybe you've already done it, right?