Discussions

I'd like to try to explain the "extra drive" thing a bit. Based on the numbers you reported for the size of your "drives", it is apparent that you do in fact have one physical drive, partitioned into two drives. When you look at the drives in "My Computer", you will in fact see two drives, but this is just visual. Think of it as having an apple pie. You can cut it into a number of slices, but it is still one pie.  
 
If the PC "crashes", you can re-format the "C" drive, and re-install Windows and all your programs etc. I do it this way on every PC I have. Having said this, because you still have but one physical drive, if that drive suffers physical damage, you have trouble.  
 
Even if you install two separate physical drives, (I do this as well) software issues can corrupt data on that drive as well.  
 
In most cases, the crashes you speak of are Operating System related (Windows), and generally have little to no effect on the integrity of the data contained on the "D" drive.  
 
Now there was also mention of moving files from the "C" drive to the "D" drive. Moving data files is fine, but DO NOT move OS files. Rule of thumb, if you didn't create it, don't touch it.  
 
Finally, I'd say you should be backing up anything and everything important to an external drive of some sort, be it either disk, flash drive, or external hard drive. Do this before you have more trouble.  
 
feel free to PM me if you would like to discuss further.  
 
Regards