Whether you formatted R or not, Windows 7 placed its boot files there when you reinstalled it to C, because C is Logical and boot files cannot be placed on a Logical partition.
I will give you the steps to fix this, but you need to decide if you'd like to have C in the first partition slot which is preferred for Windows 7 since it is closer to where the disk reader parks. If so the steps given below to convert Logical to Primary and recover the System MBR into C should include Resizing C into deleted R space.
Download, burn to CD and boot free Partition Wizard bootable CD
, select 1 for screen res, rightlick C>Modify>Convert to Primary, OK. Next rightlick C>Modify>Set to Active, OK, Apply steps.
If you want put C Windows 7 in the first partition space, next rightclick R>Delete, then rightclick C>Resize, slide left border all the way to the left over deleted R, then resize right border as desired, OK, Apply steps.
If you want to leave R where it is, rightclick R>Modify>Set to Inactive, OK, Apply step.
Now confirm from booted CD that C is Primary marked Active and if R still exists it is Inactive.
Windows 7 will not boot now. Boot the Windows 7 DVD Repair console, click through to Recovery Tools list to run Startup Repair up to 3 separate times with reboots until Windows 7 starts.