I used to have a dts that had a sql server authentication connection. Basically, the userid password is stored in the package itself. Now, when I go to SSIS, the password is
The designed behavior in SSIS is to prevent storing passwords in a package, because it's bad practice/not safe to do so.
Instead, either use Windows auth, so you don't store secrets in packages or config files, or, if that's really impossible in your environment (maybe you have no Windows domain, for example) then you have to use a workaround as described in http://support.microsoft.com/kb/918760 (Sam's correct, just read further in that article). The simplest answer is a config file to go with the package, but then you have to worry that the config file is stored securely so someone can't just read it and take the credentials.