Check Disk checks disks for errors. The small, free tool offers the choice between a standard and a complete test. Check Disk analyzed any hard drives and uses the Windows API function. The freeware checks in the full test, the media, among others for bad sectors and marks them. Check Disk supports all hard disk systems, IDE, SCSI and RAID through to connection via USB. No installation is necessary. The freeware works out well from a CD or a USB flash drive.