It sounds like you may have bad sectors on your hard drive.
Basically, the metal platters inside the unit itself are beginning to wear. The areas with wear sufficient to cause "unreliability" are not trustworthy, and such areas are starting to crop up. Windows probably has noticed that it cant read certain disk structures reliably, because they are stored on affected sectors.
Having a corrupted folder is a strong indicator of having a serious underlying problem. (NTFS is a journaled filesystem. Random acts of filesystem corruption that used to happen in the windows 98 era, simply dont happen now. There's a safety blanket baked into the filesystem to prevent that from happening. When it happens now, it';s because "Yo, Some REAL SHIT is going down!" with the insides of the hard disk. (Either you dropped it on the ground while it was running, it's just getting old, or there was a major power interruption while it was doing something important, etc...)
If chkdsk reports any bad sectors after the aggressive scan I suggested, it means your HDD is genuinely on its way off this mortal coil. Getting the unreliable sectors marked BAD by the filesystem will keep windows from using them again, and is a stopgap measure. More sectors will go bad pretty soon, and the drive's integrity will continue to degrade. Replacement is the best solution in that case. It could just be general filesystem corruption and not physical HDD deterioration though. Pay attention to the results of the scan.