The only way to convert non-destructively is using Partition Wizard old version 4.12 downloadable from here:
partition wizard 4.2 free.zip - Windows Live#
From PW Disk tab>Convert to Basic.
Back up your files and a Windows 7 backup image first:
Backup Complete Computer - Create an Image Backup. Use external HD, another HD, DVD's, another computer on your network, or 25gb of free storage on Skydrive with each Windows Live ID.
Afterwards post back a screenshot of your full maximized Disk mgmt drive map with listings and tell us what you want to do, we will give you the exact steps using PW.