HELP! About my HDD

Hi! Well I have a little bit old HDD which is just 40gb (yea its pretty low) and I am using it with my another HDD which is way higher than that one. Now, a few weeks back I saw it 40gb but just yesterday, I saw it go down to 37.5gb.. What do you think happened at it? Sorry kinda clueless…
Answer #1
HDD manufacturers don’t use the binary system, so 40GB = 40,000,000,000 bytes.
Windows will read that as 40,000,000,000 (40GB in non-binary) / 1,073,741,824 (1GB in binary), and the available space will be ~37.25GB.
Answer #2
Oh I see.. Thanks
Answer #3
I thought the problem is undetected.. sounds funny mate.. but the question is.. if you compress a 10 gb file.. you’ll get 965 mb.. but the file size is actually 950 or something lesser.. like pendrive.. the size is 8 gb but the real size is just 7.7/7.8/7.9..
Answer #4
Nothing funny about it… explained it very well…
Answer #5
Nothing funny about it... explained it very well...
posted well-detailed.. but there’ll be more that keep asking.. so, to ease the problem.. use the pendrive as an example..