My 2.5 cents worth...
Just to get a tad bit more technical. mounting it to the frame of the computer does several things. First the frame it's mounted to becomes a heatsink of sorts. Second it provides an earth ground to give static discharge somewhere to go. And lastly it keeps liquids and another things from getting on and in the drive. So yeah when you get back to the putting the drive in the machine mount it where it should go.
And I can relate to how much getting it in can be a pain. They must have colabarated with Compaq as to how to make cases. LOL