There appears to be a 2nd hard drive in your system that hasn't been setup yet.
If you know this to be the case, and you know that there's no data on the drive that needs to be saved - then go ahead and answer OK to initialize the disk (this will wipe EVERYTHING off of the hard drive). FYI - you'll use the MBR setting.
Then you can format it and use it as additional storage space.
If this is not the case, or even if you're not sure - then go ahead and open another topic.
This sort of thing happens most often with hardware problems - and if this is an external USB drive it can also be caused by the cable, the PCB card inside the external case, or even by the HDD inside the external case.