Hi Mike, usually your D: drive is reserved to your recovery files.  I suspicion you've been saving files to the D: drive instead of the C: drive.  I know it's confusing but they are on the same hard drive.  If you have unallocated space you can use a program like Partition Magic to assign the unallocated space, but you'll want to allocate that to you C: drive.  You can check the available space by going to "START" "MY COMPUTER".  I think that's what you're seeing - not "unallocated" but "Free Space".  If you have been saving music, videos or photos to your D: drive you can move them to your C: drive using Windows Explorer (START, PROGRAMS, ACCESSORIES, WINDOWS EXPLORER.  Moving them to you C: drive will fix the warning message.  If you're unfamiliar on how to do this you can email me (shopbruce@gmail.com) and we can see if we can walk you through it.  Hope this helps!
                 Bruce
                
 June 2008