Most likely... When I have encountered that sort of issue .. the Drive was formatted under FAT32..

it may not be a hardware issue -but it is a good idea to check - SMART analysers are handy for this..

the issue was probably a bad shutdown since the last defrag..

and agree with other comments chkdsk is not so friendly to user data..

I won't add my regular programs.. the list of test progs given is sound..

My feeling from the limited information... is certainly backup your data.. - use a WIn PE based live CD (Winbuilder et al) if your only comfortable with Windows.. to back up your data..
Do a clean install of windows.. BE SURE TO FORMAT THE HDD UNDER NTFS.. restore your programs.. then your data..
You may be able to get away with a repair install.. but the long term issues are not worth the little extra time in the clean install..

If there is information that you have not provided that may indicate a drive failure.. like recent new/unusual grinding and clanging noises.. then replace the HDD by all means..