Computer System Drive Full!

Help: I’m not very knowledgeable regarding internal computer workings.
I have a computer which is dedicated to my home music setup. My System C Drive (99.5 GB) on which I had Sonar Platinum installed is virtually full. I have a Data D Drive with little on it and 350 GB of space.
It would seem sense to me to move Platinum and all my associated files over to the D drive so that it basically runs from there. Is this possible and what files can I/should I move over to the D Drive for it to run smoothly - or am I talking nonsense?  
Any guidance would be most welcome.
Thank you.
 

You might also want to see about cleaning up any Command Center downloads.
 
http://forum.cakewalk.com/A-reminder-to-clean-up-your-Command-Center-download-folder-m3435314.aspx
 

I just had to upgrade my old SSD C drive to a 250 GB as it was almost always creeping up over 80%. This is not good and they run real slow. 
So easiest solution is upgrade that C drive. Is it a partition of the other drive? You can increase partition size with special drive utilities, I think Ease US has one. 
 
But for sure take all the content of the CCC download folder and copy it to an external drive and then delete it that might be all you need to do. 
 
But this is a good time to have a brand new C drive if you plan on keeping Sonar going for as long as possible. 

Here are some quick and easy ways to free up space on your C: drive.
 
1. Move your paging device
Go to system settings and find "Windows appearance and performance" (or something like that). Click on the Advanced tab and then the Change button under Virtual Memory. Remove the paging file from C: and configure it for D:. Just that easy, and you've gotten several gigabytes back.
 
2. Clean up unused files
Next thing to do is delete temporary files. Windows has a tool that'll do that for you. Go to "Storage" in system settings and look under "Storage Sense". That's a background process that helps tidy up unneeded files. I don't use it, but I do manually run the cleanup periodically. Click on the Storage Sense settings and click the "Clean Now" button. If you enable the "delete old Windows versions" you might reclaim a gigabyte or more.
 
3. Move the Downloads folder
Also look around for folders that you want to keep but don't necessarily have to be kept on the C: drive. One candidate is your Downloads folder. That can accumulate a lot of stuff, but stuff you might want to hang onto, such as installers. Create a Downloads folder on the D: drive, copy everything over there and then tell Windows that's where you want future downloads to go. Open any Explorer window, select Downloads in the left-hand column. Right-click and select Properties. On the Location tab, type in D:\Downloads. (There's a "Move" button there that I've never tried; it may move the contents of the old location for you, saving you a step.)
 
I just checked my Downloads folder. It has 156 GB of stuff in it! Good thing it's not on my C: drive.