Hi, before you proceed with re-partitioning, I would recommend creating a System Image first.
You are aware that Windows 7 creates a 100Mb boot partition. You can verify your existing partitions via Computer Management / Disk Management. It's from this area that you manage partitions (wihtout using 3rd party apps). So for example you Right-Click C: drive, select Shrink, then Right-Click on the newly created partition, format it and give it a drive letter. Be very careful with all this as C: is the Boot, Page File, Primary Partition. If it is feasable, leave C: alone and purchase a secondary Hard Disk - SATA 1Tb is cheap nowadays