Can i install windows on this?

I would google windows on chromebooks. I tried to put in a link but newegg doesn't permit it. I doubt if Windows will run on Chromebook although there are workarounds that only work so-so. If you want Windows, why not buy a windows machine?

What does refurbished grade c mean?

Search on Refurbished in the Customer Service section on this site and you'll find: B grade refers to units that may have dents, chips, or scuffs on the body. The keyboard may be shiny or worn down and hair line scratches or scuffs may be on the screen. C grade refers to units that may have dents, cracks, chips, or scuffs on the body. The keyboard may be shiny or worn down and there may be scratches or dark spots on the LCD screen.