Lg external hdd hxd5 usb 3.0 500gb is now 31 gb

So what happened right before you noticed this? Is it possible that you actually used up so much space without noticing?

Well i figured the issue.. i had windows 7 ultimate 64 bit, before. then i installed windows 8 pro 64 bit, and i made a backup, so i don't lost all my files etc. and then i used it on my lg external hdd. so then it happend.. 31 GB..... i used my hdd on another pc. still the same size.. 31 GB. i formatted, and again the same.. 31 GB...

i don't know what to do...... ;(