From http://www.iliumsoft.com/support/article/AA-01577/0/FAQ%3A-How-do-I-do-a-silent-install-of-eWallet-on-Windows-PC- :
"eWallet 4.1 and higher supports silent installs. The command-line options are /SILENT and /VERYSILENT. /SILENT will run the installation with a displayed progress window, and /VERYSILENT will run the installation without any graphical feedback.
Note that eWallet may launch at the end of the install, along with the Getting Started help document. Currently, there is no way to prevent this."