In SharePoint 2007, when a new item is added to a list or document library, the !new icon is displayed. By default, this is visible for two days. Using the stsadm commands below, you can change the number of days to display this, or not to display it at all.
Get the current value of days
stsadm -o getproperty -propertyname days-to-show-new-icon -url http://site.company.com
A value of “2″ should be returned.
Set the new value of days
stsadm -o setproperty -propertyname days-to-show-new-icon -propertyvalue 7 -url http://site.company.com
Change the value after -propertyvalue to your required number of days.