A friend of mine has a 2009 iMac presently running OSX 10.5.8 (Leopard). He has just purchased a new printer that requires at least version 10.6 (Snow Leopard), as there are no drivers for the new printer that he has purchased. I have a Snow Leopard "Install DVD". Can I just put this in his machine & upgrade, or will his machine be somehow compromised? When I click on software updates on his machine it advises that he is up to date.