Today I was called on to help locate an SSD for a users laptop upgrade. After some minor disassembly, we realized that the E7240 is equipped with a mSATA SSD (mini-SATA) more here at Wikipedia.
The actual location of the drive can be found underneath the main cover on the bottom of the device.
Remove the battery, then remove the two holding screws.
There is also a second mSATA bay. Ive not done any research on this yet, but it looks to be an expansion bay for additional storage.