You pays you're money and take your chance. Many will be proper legal copies but many may be hacked.
If you just want to try it when not go for a demo of it downloaded from their website or on the coverdisk of many magazines.
Personally I have stuck with Nero 6 as Nero 7 had a lot of problems, of course that was some time ago and they may have solved all the problems but Nero 6 does all I ask of it and is rock steady.
You could buy something like this click here but be aware theres different versions of Nero 7 and its damned confusing as to which you want, notice the print on this one at the bottom for example, some parts are only a trial.
I would also check with Novatech about the OEM part of it as I'm sure this is meant to be sold with hardware.
Downloading the demos the easiest option.