The most common misconception about renting laptops is that you will be able to rent one at Media Services. Although Media Services has a desktop lab, they do not rent out laptops to students.
However, both Copley Library and Serra Lab rent out laptops. Both Copley and Serra will let you rent out a laptop for 3 hours at a time.
It should also be noted that there are a variety of school labs that have open access for students. The following link displays both the labs and the times they are open.