I think I got it.
To everybody who is interested: just share my knowledge ***AS IS***

How to run a silent mode installation:

Edit the Abcpy.ini (this file is in the same directory as "Adobe Photoshop CS2.msi")
Modify the "OEM Install" section
Code:

[OEM Install]
SERIALNUMBER=1234-5678-9012-3456-7890-1234
SERIALNUMBERTRYOUT=
USERNAME=Your Name
COMPANYNAME=The Company
INSTALLDIR=


How to suppress the Registration dialog box:

With Orca, open the installer "Adobe Photoshop CS2.msi"
Create a new transform file
In the column "Table", go to "Registry"
Add four keys
Code:

Registry  = Custom1
Root      = 2
Key       = SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\[ProductCode]
Name      = EPIC_REGS_TYPE
Value     = #00000004
Component = Reg_HKLM

Registry  = Custom2
Root      = 2
Key       = SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\[ProductCode]
Name      = EPIC_REGS_STATE
Value     = #00000002
Component = Reg_HKLM

Registry  = Custom3
Root      = 2
Key       = SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\[ProductCode]
Name      = EPIC_REGS_LANG
Value     = #00000000
Component = Reg_HKLM

Registry  = Custom4
Root      = 2
Key       = SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\[ProductCode]
Name      = EPIC_REGS_COUNT
Value     = #00000000
Component = Reg_HKLM

Little explanation
  • Registry: Choose a name
  • Root: (this is how I think it is...)
    0 = HKCR
    1 = HKCU
    2 = HKLM
    3 = HKU
    4 = HKCC
  • Key: Do not forget to delete the preceeding "HKLM\"
  • Name: The Entry name in the registry
  • Value: The value for the Entry
    If you want to add a DWORD (like in this example), you will need a preceeding #-sign
  • Component: I get the impression this can be different depending on the MSI. In this case, "Reg_HKLM" seems to work.

Now launch your installation, p.e.
Code:

@msiexec.exe /i "\\Server\Share\Deeper\Adobe Photoshop CS2.msi" TRANSFORMS="\\Server\Share\Deeper\Adobe Photoshop CS2.mst" /qb!

Or create a group policy in your active directory that you only apply to a group of (users or) computers.