The installation cab files are 'merged' from the original media (CD or else) (197MB), then copied to the user's %temp% folder, under the 438d1ac8_d88e_46eb_ba69_11fef34cce74 directory. The '438d1ac8...' folder has 80 files, 12 folders and a size of 406MB (425,860,066 bytes). One must copy this folder along with the Config.xml file (one level up in the '%TEMP%\XSetup_...' dir) during setup to another location on disk before setup deletes it automatically.
Once the '438d1ac8...' folder with the merged files and the Config.xml are saved elsewhere, move the Config.xml file into the '438d1ac8...' folder and renamed the folder to 'Expression.Web2', place it on the network, and invoked Setup.exe. You should not need the /config flag if the Config.xml file is in the same folder as Setup.exe.
You can use the above method outlined by "ewmalmbe" for the install however in order to uninstall the Product silently you need to create a new file called UninstallConfig.xml, saved into the same folder as the setup.exe, with the following contents.