Refurbished PC

I recently put an order in amazon.com for a refurbished HP PC (tower only) for 500 bucks. I feel good by ordering from them since I save about 130 compared to if I buy it from retail. However, i feel wary about buying a refurbished PC. I wonder if any of you ever have any problem or know anybody who ever experienced bad things from buying a refurbished PC.
 
Amazon didn't ship the tower yet, so i still can cancel it and buy it brand new from best buy.

i don't think there is nothing to worry about if it is only the tower. a tower is just something that houses all of the components.

It's not only a case that i am talking about, it's actually a working CPU tower, so it already has all of the stuff needed to run the computer. my concern is that the CPU tower is refurbished, not brand new. I'm also iffy thinking that if there is a problem with it in the future, it will a hassle to return it or to get it serviced if I bought it from amazon.