when you set up a ssd you want to do some thing that turn off things like swap file. http://www.overclock.net/t/1156654/seans-windows-7-install-optimization-guide-for-ssds-hdds
the swap file and other setting will eat up space on a ssd. with ssd there should also be a clean up tool from the vendor that take empty blocks and wipe them and let the system reuse the data. most ssd set some space for trim and garbage collection.