As the HDD (320 GB) is bigger than the SSD (120 GB) it was recommended that the HDD be shrunk to a smaller size than the SSD. Using Windows 7 built in disk management, it is unable to shrink the HDD to anything smaller than 160 GB.
After running defrag, removing restore points, re-running defrag again, installing Defraggler I learnt that the Master File Table (MFT) is located roughly in the middle of the drive hence why it won't shrink to anything less than 160 GB.
Some more specific deltails:
- Windows 7 Professional 64-bit
- TrueCrypt encryption is on system drive