Is there an alternative to 'chkdsk'?

The defragmenter doesn't check the disk - you're counseled to run chkdsk before you defragment.

And no, there isn't an alternative to chkdsk. It's the only one that checks the file system. Although there are quite a few other tools that check the hard disk itself, sector by sector, none checks the integrity of the file system as well as chkdsk.

SpinRite, from GRC, is a very low-level hard drive maintenance and recovery tool. It isn't free ($89 for first-time purchases), and it is not terribly pretty, but is very advanced. The UI (and their website) needs some design help, but they have the tech side of things down.

DFSee (€49) is not for the neophyte but looks comprehensive (i've never used it). DFSee is a generic disk, partition and filesystem utility for maintenance and data-recovery.

Hard Drive Mechanic is another commercial, but slightly less-expensive ($69), product option.

Other choices include SeaTools from Seagate and Western Digital's Data Lifeguard.

You could try the (very-small-footprinted: 192KB) Emsa Disk Check software.