I recently added a 120 GB SSD to my PC and mirrored the system on my 500GB HDD. When that happened it ended up reserving 40GB of the SSD to the system. But the system is on the other 80GB. So now I can only use 2/3 of the SSD.
Also my 500GB HDD has “lost” 100MB, which would be nice to have also.
I’m running Windows 7 x64 bit.
Here is an image of my Disk Management: