I am sorry if I didn't get your question correctly but If you mean what does "bare drive" mean, in means that it's the drive only. You have to put it in your PC Case and connect the cables. bare drive vs. external drives which come with a case and you connect them usually through a USB cable. If you mean the capacity I got the 2 gig version = 1.8 gb

Do these come with SATA III cables to connect to your motherboard or do you have to purchase those separately?

**Note** There is no distinction between SATA I/II/III cables. Any SATA cable (quality, not junk) will work with all 3 standards, just as fast: http://www.serialata.org/documents/SATA-6Gbs-Fast-Just-Got-Faster.pdf

how do you get it to boot or install a OS on it when it says

With the drive installed and a SATA line plugged in along with the power connector you then turn the power on. As the machine powers up you will be given the opportunity to get into the BIO's by hitting the DEL key. Once there make sure that the drive is recognized by the BIO's and that you have made the changes to date and time and that you DVD/CD player/recorder is recognized. Place your WINDOWS or LINEX operating system disk in your DVD/CD then follow the directions. The operating system disk will format your hard drive. PS don't forget to set the BOOT order so that your system will boot off of the DVD/CD drive. Set your hard drive as second boot device. Once the operating system is installed power down and then back up so that you can reset the hard drive to 1st device to boot from and the DVD/CD to 2nd boot device.

It's pictured without a cover to somewhat seal the hard drive discs. Does it come with the cover?

The hard drives arrive fully enclosed and ready to use. Not sure why the photo is posted the way it is, however you will have no issues.Hope this helps.