You can use win32DiskImager (free download) to make a copy of the card's image onto your hard drive. You can then use the same program to burn the image onto a new card.
I have found that all cards are not the same, one that says it is 32 GB may not be quite 32 GB, so sometimes you get a "insufficient space" error when burning to supposedly the same size card.
If this happens, you can go to the next size bigger card to burn the image to.
Read up on how to use the win32diskimager, if you are not careful, you could wipe out the card you are trying to copy, since this program does both copy and burn.
And I agree with JDFan. Dont copy illegally, however, IMHO, making a backup copy FOR YOUR OWN USE, is ok in my book, since there is a chance the SDCard could get plastered and you will need to restore it.
It's kinda like making a backup of your PC's hard drive.
As far as the guy you bought it from selling illegally copied roms, thats a whole different matter.