The module shown in your list is a 4GB module, if you have 4 of those modules then you only have 16GB.
What you have bought is two 8GB dual-channel kits. The kit means that it will provide a total of 8GB.
High-performance 8GB Vengeance Dual Channel Kit, 1600MHz, 9-9-9-24,
1.5V Key Features
Two 4GB memory modules
It may well be that you have a memory limited edition of Windows and may need to upgrade to a higher edition to use the extra memory. Windows 7 Home Premium 64-bit has a limit of 16 GB. Windows 8 (standard) is limited to 128GB
From Windows Physical Memory Limits:
Version Limit on X86 Limit on X64
Windows 7 Ultimate 4 GB 192 GB
Windows 7 Enterprise 4 GB 192 GB
Windows 7 Professional 4 GB 192 GB
Windows 7 Home Premium 4 GB 16 GB
Windows 7 Home Basic 4 GB 8 GB
Windows 7 Starter 2 GB N/A