either lost or corupted data

so i bought new PC and use my old HDD and secondary drive on this machine ( external ) everything was fine till one time i couldn't access it completely . i ran chkdsk it fixed itself. now today i couldn't access only certain folder in that drive ran chkdsk again i can access the folder in question but it doesn't show all files i miss few folders from there . any idea what might be the problem ? that HDD always was used as secondray drive and mostly as safe storage for my files . thnx edit- chdsk again log said no bad sectors found nothing changed ran Pandora recovery found photos but deff not all now runing HDD regenarator 1.71 but only to see if got any bad sectors since it not full version HDD recovery found 0 bad sectors any idea what might have happened ?

if you're sure you are not virus or malware infected then I guess it your hdd having hardware failure so if I were you I'll start backing it up. just to make sure.

it's realy weird since it's only was used as storage HDD on both PC's and not a lot data was transferred and only started getting problems when i started using it as external drive ( using external drive enclosure ) . i suspect there might be problems with connectivity but not rly sure how to check if my USB or enclosures connections messed up. don't want to open up my PC case to conect it straight since still got warranty on PC lol

u can lock this topic ty