Card to download games for DS's DS Lite

[DrSeuss]

Advice please. A friend says I should purchase a card from ebay to download games for the DS Lite we recently got second hand for my son. Another friend says she did this and that the soft ware was incompatible and broke the DS. Has anyone any experience of either a DS being ruined by this or successful use of a card. The DS was a much anticipated reward for effort at school for my son and he adores it. I'm all for cheap games but daren't risk ruining his much loved toy.
Thanks.

I can't see how the card will break the DS. Many many people have used these cards.

However, it's worth pointing out that it is now illegal to sell these cards in the UK and furthermore, downloading the games without owning the original is also illegal. So in that context it's probably not a good idea to discuss them in great detail here. There are other forums for that.