Install Microsoft apps that require SP2 without installing SP2

Launch regedit.exe
Go to HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Windows
Change the CSDVersion value to be 512 or higher (0x0000200 in hexadecimal)
Close regedit.exe and install for example Visual Studio 2005
Rerun regedit.exe and change the CSDVersion value back to what it was originally

NB Don't forget to restore the CSDVersion, otherwise your PC won't boot after a Windows Update

More info: Aaron Sebner's Weblog