This is pretty much a waste of precious database space and above all speed. You'd better add the possibility for multiple systems in the system column, like this:
|-------------------------------------------------------------------|
| ID|----Title----|-----News-----|--Date--|------system----|
|1|---Test-------|----BLAH------|051008|------MAC,PC,UNIX --------|
Then have your PHP script split the comma's into an array or however you'd like to use it, like this:
$query = mysql_query("SELECT * FROM `news` WHERE `ID`=1"); // Obviously change the ID into something dynamical or however you fetch the news now.
$news = mysql_fetch_assoc($query);
$systems = explode(",",$news['system']);
This will give you an array $systems, in which you can check wheter the system you want to display is in there.
