External hdd not displaying files & different from most issues

hello there...

have got an external hdd issue quite similar to most other complications I have come across on this forum... all files and folders amounting in size to 776 gb on my 1 tb hard drive which is technically 931 gb, seem to have dissappeared but the properties and scanning shows all files right there in the drive....... i've tried most remedies i've skimmed through this forum like "Show hidden files, folders or drives" and finally the ATTRIB -H -R -S /S /D I:\*.* with I being my HDD....

In addition to $RECYCLE.BIN , RECYCLER and a desktop configuration settings file , there is a THUMBS.MS file.

entering the ATTRIB -H -R -S /S /D I:\*.* in command prompt yields the following response

Access denied - I:\Thumbs.ms\com1.{d3e34b21-9d75-101a-8c3d-00aa001a1652}
Access denied - I:\System Volume Information



i have no idea wot to make of it..i sure hope its no malware attack...
all help appreciated in advance...needless to say at this point my data very precious...
eagerly awaiting helpp....