I currently have two hard drives installed into my desktop - one with the OS and one without. However, it seems that I can not access the second hard drive for storage. Whenever I check the 'My Computer' page and look under 'Hard Disk Drives', it'll only list the one with the OS installed.
Whenever I boot from the hard drive with the OS, the computer works perfectly. However, whenever I boot from the other hard drive, it'll just be stuck a blank screen with a flickering _ near the top left corner.
Any new empty HDD needs two things done before it can be used. You must Create a Partition on it, then Format that Partition. Some systems integrate those into a one-step "disk initialization" process. When you Install an OS on one drive, those processes are done for you so you may not recognize that the work was done first. However, it sounds like you may not have done that for the second HDD.
Now, you say you "found a solution", but appear to be missing 70 GB. So what did you do to gain access? Maybe you actually did Create and Format a Partition, but the default settings used made a Partition that did not use up all your HDD's space. You can determine this by examining the HDD's in Windows Disk Management in its LOWER RIGHT pane. If it shows you there that the second HDD has one Partition of the size you know, plus some Unallocated Space, that is what happened. For that you have two alternatives. The simple one MIGHT be to let it be that way. You then just RIGHT-click on the Unallocated Space and tell it to Create a new Partition there using all space available, then Format it. You will end up with a third "disk" with its own letter name to use. On the other hand if you don't want that AND if you can afford to lose all the data on the existing Partition that is too small, there's a better way. In Disk Management RIGHT-click on that Partition and Delete it. Now right-click on all that Unallocated Space and Create a new Primary Partition that is not bootable, and make sure it includes ALL the space available. Then Format it. Now you'll have ALL of the second HDD as ONE "disk" of full size.
Wait! I just thought of something. You did not specify the HDD size. If it is a 1 TB drive, what Windows will show you for "Free Space" on it when empty is about 930 GB, so you might think 70 GB is missing. It is NOT.
A 1 TB drive has 1,000,000,000,000 bytes capacity, approximately. But Windows defines "Gb" as 1024 x 1024 x 1024 bytes, or 1,073,741,824 bytes. Using this as "1 GB", there are 931.32 of these in exactly 1,000,000,000,000 bytes. You did not lose space. Microsoft is simply using a different "yardstick" to measure the space from the measurement system used by the drive manufacturer. If that is your situation, do NOT make any changes to your HDD. It's all there already!