Why would you install to RAID when you have an SSD?
If Windows 7 will install to the RAID (a big if) you will be given the choice of which partition you want to install upon during the Custom install, as shown in these illustrated steps: Clean Install Windows 7.
Or you can choose to delete any or all partitions and repartition as you desire using the Drive Options (advanced) choice also detailed in above tutorial.
As long as you don't touch the partition where you have your data, it should not be affected. You can label the Partition earlier in Disk Mgmt, or judge by size which it is during install.
But this is not a recommended method as one should always have the data backed up externally to be safest.