I used to see this 1 or 2 times a week years ago, all because people didn't have a backup regimen e in place.. and learn the hard way... and most had a "million selling album" they'd lost.. oddly I saw none of them on TV after ;-)
 
with regard to recovery http://www.runtime.org/  as for the drive, it depends if you can free up space elsewhere.
 
http://download.cnet.com/...0-2248_4-10139400.html
 
(tree size free by jam software)
 
 
will give you bloat area's that you might be able to claw back some space
 
I have an external caddy, so you can hook up a 3.5 or 2.5 drive.. and free up space to that drive also.
 
obvious things like ccleaner, will help claw back a bit of space..
 
but well instead of ranting / venting saying if it was a laptop drive/system drive would have been far more helpful. also if other none music stuff e.g. games were installed that you can remove to get rid of ( / reinstall later)  that eat lots of space.
 
personally I'd attempt recovery to a new bigger drive.. but make that drive the slave one, so nothing more was written to it.. and boot off a 3rd drive.
 

Anderton

robert_e_bone
 when hard drives fail, there is a good chance that it is a failure in the circuitry, rather than an actual physical media failure, and there are expensive but available service companies out there that can recover data from that kind of failure.

I buy hard drives in pairs. That has saved my butt a couple times when I was able to remove the platter assembly from the non-working drive and connect the electronics from the working drive long enough to back up the data.

Looks like you should be looking into mirroring your hard drives :) RAID 1. Cheers..

Some error codes are generated by the application; Then, the others are by OS (Windows)
"disk may be full" error happens in other applications as well; so it is most likely Windows.
When a disk is actually full to capacity Windows will error code: 'paraphrase'; "there is not enough room to save your data"
The most likely fault with "disk may be full" is when the MFT (master file table) on the hard drive becomes corrupted.
Every program type uses its own extension to write to the MFT. In Sonar's case .cwp etc.
Both the application and Operating System tries to work in harmony to preserve this integrity.
But "schitz happens". It used to be when this stuff begins happening too much, means the hard drive is beginning to malfunction.
As a note to myself; I never got schooled/learn/train on the operation of these newer SSD drives; but to think, for backwards/legacy purposes it has to be similar. 
Best practice is to 1: Save periodically 2: 'Save as' often as significant changes you make to your project. This in effect generates a new or a rewrite of the MFT file.

js516
My projects are more valuable than disk space. :)

Regardless of the technique used, this is IT in a nutshell.
(see what I did there?)