Crash on MS Backup, ScanDisk failure?

Only trainee techie, but had real problem: Tried to Backup Office Desktop (stand alone) PC (Athlon 1GHz, 256M RAM, 40G HDD) running ’98, prior to upgrading to 2000. No Tape backup available, so backed up onto C: (39Gbte avail.. Bakup copies files OK but crashed 98% of Verification. Thenceforward would only start in Safe Mode. Tried many things, but finally had to re-install ’98, which worked fine, but therafter insisted on ScanDisk Surface scan on every boot, which also crashed on 2%. System stable if ScanDisk skipped. Anyone have any suggestions?