The easiest thing to do (and therefore what I would do) is to clone your 500 GB drive to a fresh 1000 GB drive. You will have what you have now, plus over 500 GB free space. You can then continue working, and worry about freeing up space later at your leisure.

Had to laugh as all my system drives are only 240GB SSD. I just checked and my 2 DAW machines are only half full ( 120 GB ) And I have a crud load of software installed. I also generally do not re direct sample libraries.. only DIM Pro and my Air xpand are on my 1 TB data drive along with back ups and movies etc. 
 
I don't record to my SSD C drive as a tech told me they should not be written over and over.  I don't store any data there. Most my stuff is in One Drive and Drop Box. I record directly to  a 3rd drive a 240 GB SSD that is pure CWP folders. Taking the techs advice I will just swap it out every couple of years, put it aside as a backup. 

Cactus Music
Had to laugh as all my system drives are only 240GB SSD...

 
Same here. My previous one was only 110GB and that was easily adequate. But I've got several larger drives for non-OS stuff and I'm fussy about how I organise it all.

To clone that drive, Acronis is your answer.  However, with that said, I have moved all larger files, wavs and Kontakt stuff to an external drive.  Had to go in and change a few paths, but that is a simple solution.  You should have no problem is you work that way.

Like Cactus Music, my SSD's are about the same-250GB and less than 5 used-about 96GB used. I do have multiple hard drives. But I have many apps. That's my desktop.
 
My Asus laptop is the same. I removed the CD writer\reader in my laptop and installed a second hard drive in it's place.
Very easy to do.

Macrium Reflect is an excellent backup and restore utility, and it allows you to "clone" or prepare a new hard drive directly from a backup file on one of your many backup drives.  You do take backups, yes?
 
This is wonderful because if you ever have a hard drive go pear-shaped, it may already be too late to start thinking about cloning it.
 

Cactus Music
...I don't record to my SSD C drive as a tech told me they should not be written over and over. 

I too don't write to my C partition, but that's for organizational purposes rather than performance or to increase life expectancy of components.
 
Besides that, the write-durability of SSDs hasn't been a serious issue for real-world use.  Not even when you direct your Windows swap file onto an SSD, and not even when you turn on Bitlocker.  For some interesting reading, please see this article on the big murderous SSD endurance test done some years back. 
 
For me, it's more important to be taking BACKUPS than it is to worry about wearing out my SSDs.

I cloned my HD to an SSD (Samsung Evo) in Windows 10. It was very easy indeed. You just need an external HD case, plug it into your USB port and fire up the bundled software. The second time I came to clone my HD, it was SSD to SSD....my god it was fast.  The cloning process took so much less time.
 
Regarding your 500 GB driving getting full up, you might want to do what everyone above suggested, clean out old download files. Every time you update plugins, like iZotope products, they leave a download file on your computer. These files can get pretty big and, if there are duplicates, they will quickly fill up your computer with setup files.  I have an external 1TB drive where I keep backups of the most recent setup files (just in case), and periodically clean out the old setups.  The same goes for downloaded samplers, sample files, vst instruments etc. If they were downloaded, chances are they have left a trace somewhere on your computer taking up precious space.
I'm surprised you are running out of space because I use a 256 GB drive and still have space, and I've got Sonar 4-Platinum (+ all instruments) installed along with Bandlab, various other DAWs and some big sampler programs such as Kontakt (+extra samples), Addictive Drums (+extra kits), tons of VSTs, the list goes on....Recently I decided to uninstall some of the free instruments bundled with Sonar simply because I never use them and they were just taking up space.
 
My way of working is: I keep the program files and samples on the main SSD (I work on a laptop) and run my sessions from an external drive hooked up to the eSAT port. This drive is a regular 7200rpm hhd. Why? Because SSDs have a limited read/write life-cycle, where as HHDs do not. Also, if your SSD gets corrupted/damaged, you lose everything.  HHDs, even when damaged, are usually recoverable. My son once dropped my HHD drive with about 4 years of music production on it. The drive stopped booting up, but periodically I would try it on my Linux computer until one day it sparked to life and I spent the whole day recovering what I could from the drive....it never worked again after that (one lucky shot).  Another reason to have an external drive is that you can run virtual instruments from the SSD (where the read speed is fantastic) and write to the HHD without interruption from a read process.
The only time I deviate from the above is when I'm on the move. Then I may transfer the sessions I'm working on to my SSD so that I can mix on the move.
 
Hope this helps

HO, HO, HO!
Merry Christmas to you all - !
Finally, I built in my new SSD, 1 TB large, cloned C:/ to the new one, everything ok so far. I changed the internal cables and positions of the 2 drives, took the old 500 B drive out, rebooted - and all programs from MS Office over both Sonar (with plugins), Sibelius to ProTools: all working fine and without any trouble. even a first small Windows update. And the printer. And the USB-connections. And the optical drive. All fine.
Now I shall wait until the next major Windows update, then I will delete all the stuff on my extracted drive, and insert it to have additional, fast storage. It's also an SSD, after all. 
As other members said here, it's no problem at all to do a little cloning once in a while. Thanks for encouraging me.

"My guess is this is real source of the issue - too much non-system related data on the system drive. 500GB is a big system drive. Expanding the size of the system drive instead of adding to non-system drive space for non-system data is poor disk management. Consider adding additional non-system space, if necessary and cleaning up the existing system"
Steve gave you the best answer and you ignored his advice, I'm just chiming in here so someone doing a search
will make use of the "best answer".
Keep the C drive "lean and mean", 250gb is plenty; SSD if budget allows.
Put your samples on a 500gb to 1TB SSD for fast load times. m.2 if budget and mother board allow.
Your cwp files on a 7200 mechanical drive, until write and re-write is proven to not cause "issues" for SSD's.
More than once I've seen those who wanted to put the OS on the M.2 drive; are you nuts!
The m.2 seems to load NI and SD3, before I open the project; well not literally, but still, its right now!
To each his own, but as Steve implied: for a DAW, disk management, disk management, disk management.
Disk management is to a DAW what "location" is to Real Estate.
You can thank me later...
 
T