Well, my C drive is almost full so I must move Something.  Is it OK to move my Drum Audio loops to another drive and then tell Sonar where to find them?

yes

Sure.  In fact, if you have a large amount of samples on your C: drive, they can all be moved elsewhere. 
 
You probably also have a lot of junk (temp files, logs, old installers) that can be disposed of.  Use Windows disk cleanup or a utility like CCleaner to identify and nuke the clutter.
 

Being adventurous now, Is it OK to move all of Sonar's files to another drive?  I suppose the Sonar .dll program file must be left on the C drive.  Is that correct?  Thanks.

Also, Sonar no longer can find my moved audio files.  I have updated the info in Preferences under Audio File Location.  What else must I do, please?
 
And, I want also to move my Drum MIDI loops.  How do I tell Sonar where to find them, Please?
 
Thank you!
 

Is your command center download folder on your C drive? If so, I would move the contents of that first.

timidi
yes

Good answer.
 
Short and to the point.
 
I wish I could do that, but I can't.
 
Always have to elaborate, see?
 
I'm rambling now aren't I? I just can't help myself. Sometimes a little padding out of the answer can add colour and useful background information or give some insight into the personality of the poster and therefore give the person asking the question some idea on whether or not they can trust the credibility of the answer because maybe it was wrong and the person providing it a clueless idiot ? That's not the case here, but hey it's the interwebs and nothing is real, right ? Who knows who he really is? It could be that he doesn't even know that he answered a question. Mebbe his cat just walked across his keyboard while he was busy laying down a killer guitar riff and the answer is really no and has no idea that he has just unleashed potential doom upon your pc.
 
That's why I thought it was important to add the reassurance of a second opinion. But then I might be a know nothing idiot too ? Hmm, I didn't think that through properly did I ? Oh well, at least you can be reasonably certain that a cat didn't accidentally type this one.
 
So, that's a Yes. 
 
I think.......
 
Yes, I'm pretty sure he's right. 
 
If he's not then don't blame me.
 
 
He said it first.

Marvinglenn2, some thoughts
 
What version of windows? Is it 10 and / or upgraded previously and you are happy with the upgrade use Windows Disk cleanup tool / advanced to remove all past updates + tmps etc. This could gain you GBs of space. Also make sure you have emptied out the Sonar Command Centre folder of past Sonar update setup files ( via settings, paths tab, Download path ) - will add more GB space.
 
Same might apply if you have likes of AIR or ARTURIA plugins added. They also setup folders to download install / update software that dont delete afterwards .. GB of space taken up.
 
 

Are you using a directory per song containing an audio subfolder with all audio WAVs?  If so, you can set folder location in preferences and just move the folder containing the CW files and the underlying subfolder with audio WAV files. 
 
When you say sonar can't find it the moved files - what specifically is the message and how are you trying to open them?  You won't be able to use the drop down menu from recently accessed projects, because those will be pointing to the old location.  You'll have to either click Open in Sonar (and navigate to the new location where you moved the files) or use windows explorer to open the project file in the new location. 
 
btw.. MIDI (drum loop) files are typically very small.  Moving them won't clear up much space at all.  Did you mean to say drum sample library files?  
 
Another option would be the "clean audio folder" utility to remove old / unused WAV files from projects.  Depending on how many projects / tracks / comp takes you have and when this utility was last ran, this could easily free up several GB.  A quick search should reveal plenty threads in this forum to guide you through that process.

Thank you all for your help.  I will implement your suggestions. However, my problem still exists.  My Audio Library of Drum loops is now on my E drive and I still need to know how to tell Sonar where to find it.  I'm using Win 8.1.  
 
Knowing me, I probably missed one of your brilliant suggestions that would have solved my problem but, just in case I didn't, could we please try again.
 
Thank You, again, very much!