CHKDSK is the new Scandisk, right?
All hard drive manuf. offer a FREE diagnostic utility at their sites...and they are all more effective than chkdsk.
For testing the drive itself, yes, not necessarily for testing the filesystem.
CHKDKS and the diagnostic utility should both be used.
As for fixing problems:
If its physical damage, that can not really be fixed. If its just a problem with the filesystem caused by, say, an improper shutdown, CHKDSK should be able to fix it.