Simple - look at your code:
For Each HDDDET In HDD.Get
HDD_DETLAIS = ...
TextBox1.Text = HDD_DETLAIS
Next
Each time you go round the loop you positively set the textbox content - so when you end the loop you will always show the last item you set info for.
If you have two HDDs, you will always see the second.
If you insert a USB stick, you will see that.
Decide what exactly you want to see, and when you find it in the loop, break out of teh loop by using
Exit For