The middle-priced one shipped with a Combo Drive, so you should be able to read DVDs just fine. The highest-priced one shipped with SuperDrive, to burn DVDs. When you're at the computer you can find out which one you have via system properties as described above.
Well it does read dvd r i made a copy of it at work and those ones worked fine not sure why the other ones would not read though, never mind, now have to figure out why the programs have installed properly but do not open they just bounce and do nothing, i have 10.4.7 update to put on tonight hope that makes them work?!