missing drive designation

hello, i partitioned my hard drive and it worked fine for a long time. Now my D: drive designation is missing. All of my information is still in my computer. It shows up as used space, it just doesnt have a drive designation so I can’t access it. Is there an easy way to get this drive renamed? I bought a program that allows me to extract the information but it is a very lenghty process. Thank you for your help.