Lenovo E440 11e E/Edge :: Missing Hard Drive Space

I have a newish (4/2014) Thinkpad E440 with a 500 GB HD. All of a sudden, the hard drive has filled up. I cannot account for all of the space. Here's what the system says:
 
35.2 GB available of 452 GBApps: 31.4 MBPictures: 76.1 GBVideos: 137 MBMusic: 20.9 GBDocuments: 8.14 GBDownloads: 0 bytesRecycle bin: 0 bytes 

So you can see this is a wee bit over 135 GB.  Where in the world is the rest of the space? Here's what I've looked at / done so far:
 
"System Protection" is turned on and is currently using 10.48 GB. I have the max set at 3% (13.59 GB). There are currently 3 saved restore points.  --> EDIT now it says it's using 5.97 GB and there are only two restore points now.I've run "Disk Cleanup" and it says I could regain 33.6 MB. Whoo-whooooo!The disk was 1% fragmented so I ran defrag.I ran the error checking tool on the drive and it said there were no errors on the drive. Now, after finishing the defrag, I've lost more space "as we speak"20.4 GB available of 452 GBApps: 31.4 MBPictures: 76.1 GBVideos: 137 MBMusic: 20.9 GBDocuments: 8.14 GBDownloads: 0 bytesRecycle bin: 0 bytes 

 FYI: When I go to Lenovo Solution Center and click on Support and then go to Configuration History, the calender there shows the yellow triangle with the exclamation point in it for "System Events" on every single day that I use the laptop. When I click on one of those days, it shows multiple "Application Errors". This has been going on since the day I got it.  I don't know if there is a log somewhere that is spiraling out of control.
 
I forgot to say I use Kaspersky Pure 3.0 for virus software and I have it performing a Full Scan, a Vulnerability scan and a Critical Areas scan every day. I also scanned the drive with Malware Bytes and it did not find any malware. Also I am running Win 8.1 - it came that way from Lenovo.