My computer wants me to format my second hard drive

[hondaxxx2000]

I just plugged in a second hard drive to my computer that has some stuff from my dad's old computer and when I try to open it it says this drive isnt formated for mat now. How can I just get the drive to open so I can see whats in it?

 

[Rip_Uk]

right click the drive in my computer and go to properties, then check which file system it is in.