Critical incidents - on a misterious drive

Hi to everybody!

Can someone help me to understand the message shown in a critical-incident?

It says, the file system structure is corrupted, and that I ought to run "chkdsk" on the drive "\Device\HarddiskVolumeShadowCopy4".

I never knew that I had such a drive, and I can't find out, what this could be ...

Thanks in advance,
SeaTrout