Blue Screen of Death

Workstation will not boot. Get the error STOP 0x0000007B INACCESSIBLE_BOOT_DEVICE. The OS = Winnt 4.0 with Service Pack 6. I have tried to repair the Winnt version but install is unable to find a Winnt version. The only drive that is recognized is the a: drive.
I believe the c: drive is full. Is there a way to get at the c: and clean it up, or must I reinstall Winnt and format the drive ???