Yea Ozzy38, you would have to install it yourself. Not difficult at all Just open the case, find an empty drive bay use the cable and screws that came with it. you need to make sure that you get the right drive for your computer, Serial ATA or IDE are the most common choices right now. Plug in your cables in the right slot,
There should be an install guide that comes with it that should have pictures of the corresponding slots. BEFORE you open the case make sure to unplug the main power cable and press and hold the power button to discharge the capacitors and make sure to have your arm or other hand touching the inside of the case when poking around in there. This avoids Electro Static Discharge which can turn your computer into a nice end table. Make sure to plug the 4Pin power cable into the back of the drive. Then plug in the main power cable, mouse, keyboard, monitor, and sound cables back in. Should have told you to unplug those before opening Sorry! Don't put the side of the case back on yet, you might have to get back in there. Once all your cables are back in place hit the power button your Operating system should find new hardware and ask you to install drivers off the disk that came with it! If all that goes well, you are ready for prime time. Put the case side back on and replace screws and enjoy the $70USD you just save by not taking it to a computer shop.
Gwenion1 is right, now most games don't need constant access to the disk but if you watch a lot of movies or burn disk the data transfer rate does matter. I just read an article in Maximum PC saying that Toshiba has come up with a way ti jam 80 Gigs of data on one Blu-Ray disk. That makes it a fairly cheep solution for hard copy backups as compared to tape drives. A USB2.0 external drive is the easy way to avoid installation if you are not confident in digging around inside your system though. I have used them for laptops that didn't have a Combo drive to install software but on my desktop I want that sucker inside!!