Hard drive mysteriously lost approx 170 GB

Win 7 64 bit with two internal 1 TB hard drives. The system disk had around 200GB feee . Yesterday got a BSOD reported to be a reg corruption and did start up repair. Today noticed only 30 GB free space so had lost about 170 GB

I moved an 80GB folder to other internal drive to give some space. Now have 110GB free but still missing about 90GB. I did not install anything new or add many photos. Does start up repair make a back up anywhere like the windows old made when new install of windows?

Amounts are approx. Computer is clean no viruses. Both disks are perfect according to Hard Disk Sentinel

I don't believe it makes a backup, unfortunately.

i only wanted to delete it as i thought i may be taking up the missing space

Do you, per chance, have a recent full backup image or restore point?

no image. no restore point

Have you checked Windows Disk Management to see if the drive has an added partition?

no added partition

If I understood well, you lost 170G of free space, not data.

After a BSOD you should do a check disk.
Schedule a check disk.
Open a CMD window and type chkdsk c: /f It will say that the disk is in use and if you want to schedule fo next start = Yes

If I understood well, you lost 170G of free space, not data.

After a BSOD you should do a check disk.
Schedule a check disk.
Open a CMD window and type chkdsk c: /f It will say that the disk is in use and if you want to schedule fo next start = Yes

yes 170 GB free space. Did chkdisk found and fixed problems. Did not get the 170 GB back though

I would download a program called Tree Size Free which will show what is stored on your disk and hopefully allow you to recover your lost space..
There is both a portable and install version (pulldown menu).

JAM Software - Tree Size Free

I want to see the Check disk log

Follow these steps to view the Check Disk (CHKDSK) results:

Open the Control Panel
Open Administrative Tools
Select Event Viewer.
In the Event Viewer expand the Windows Logs
Select the Application log.
Right Click the Application log and select Find
Type wininit in the box and click Find Next
In the middle pane click the Source/wininit line that is found.
In the south pane, you will see the complete log for the latest Check Disk (CHKDSK).

Select all on the south pane, copy and paste it here.