oh.. ok. just that i saw the german flag by your avatar and assumed that's where you were. sorry.
also a dvd drive is hardware and not software. can't be downloaded but you can order one through online stores and have it delivered to your home.
the safest bet though, would be to get one at a real store. you could probably do a search for computer or electronics stores in your area or just look through a phone book for one. Circuit City, Best Buy, and CompUSA are a few i can think of right now but there are most likely many more that i have not heard of.
most of the good stores can install it for you, you would just need to bring your computer with you. some will charge a small fee, while others may do it for free so when you find a store ask them about it.
if i had your computer sitting in front of me so i could see it then i could talk you through how to do it for yourself, but for me to just sit here with no reference and try to explain it would only end up causing confusion . not the kind of thing you want when you are messing with the innards of a computer
Well, if I were to buy one online, could I have a computer expert (like someone I know) install it for me? I don't have any of those stores near where I live (I bought Spore at Wal-Mart go figure...)