If I followed what you believe is your problem concerning you "C:" & "D:" drives and what issues you are trying to achieve resolution on. Am I correct in thinking you would like to find a way to use your D: drive as your primary drive, until you clear up the problems you're suffering on your C: drive? If I have understood you correctly as reflected in my preceeding statement, I would like to offer these comments for your consideration.
On most every computer I've encountered these days, D: drive is usually your CD drive. These days, it appears that the CD drive has replaced the 3.5 floppy disk drive that used to be the secondary drive on most all PC's, prior to the advent of CD drives usage on all PC's.
It used to be a common practice, if you were having trouble booting from your "C:" hard drive on a PC, that you could deflect the firmware boot sequence embedded in the PC BIOS, at the beginning of the initial few seconds, when you initiate the "power on" that triggers the boot sequence's data stream protocol. This was achieved by tapping the F10 key immediately after hitting the pwr on button. Some PC's used a different "F" key for this purpose. However, you should be able to locate the exact "F" key if you check your User's Guide hard copy.
Hitting this "F" key at the beginning of the boot sequence will divert you to a DOS Menu that should allow you to select the "D:" drive as your primary drive, thus facilitating the selection of the use of a CD that will allow the installation of a clean, uncorrupted version of your OS, from which you should be able to effectively resolve all issues that may be screwing with your PC.
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