If you try installing Adobe Photoshop CS3 on the Windows 2003 Server operating system you will recieve this error during the instalation:

The minum system requirements listed below are needed in order to run Adobe Photoshop CS3 and are not met

• Windows XP Service Pack 2 and greater
• Winows Vista

Please Upgrade or aadjust your system to meet these minumum requirements and then restart the installer.

I was a bit dismayed to read this because Windows 2003 Server is actually a more advanced OS than Windows XP.  Fortunately, there is a workaround to this problem.  What you can do is trick the installer to think that you are really running under a different OS.  Microsoft has a nice tool called Application Verifier that lets you set some of these OS constants for a specific program for testing purposes, we can use this to get around this installer issue.

1. Download and install the Microsoft Application Verifier program. 
2. Run the application
3. Select File->Add Application, the browse to the Setup.exe of photoshop.
4. Under tests check compatablity, then "HighVersionLie"

5. To mimic a specific OS, you need to modify the version settings.  Right click High Version lie, then click properties.  For XP SP2, you would type in the following values:
Major:5
Minor:1
BuildNumber:2600
ServicePack Major:2
ServicePack Minor:1