The packages themselves are stored in the msdb sysdtspackaes90 table.
It’s important to note that the SSIS
server isn’t aware of packages stored
in the File System until those
packages have been imported to the
File System folder in the SSIS
service.
...
While the SQL Server Management Studio
is shipped using the default folder
locations of MSDB and File System, you
can freely add new folders to this
structure using the Create New Folder
option. When you create a new folder
beneath the File System system folder,
a new directory will be created in the
file system. By default, these
directories are located in the
c:\Program Files\SQL
Server\90\Packages directory.
Importing packages to a File System
folder will result in the package
being copied to the like named
directory in the file system. For
folders that are created under the
MSDB folder, a new entry is added to
the sysdtspackackefolder90 table that
tracks the folder structure. However,
it’s important to realize that the
packages themselves are still stored
in the msdb sysdtspackaes90 table. The
Folders option in the SQL Server
Management Studio essentially gives
you a way to apply and organization
structure to your packages, enabling
you to group like packages together.
Managing and Deploying SQL Server Integration Services
Anyway, I recommend to install all SPs.