When trying to install sql server 2008 R2 from the SQLEXPR_x64_ENU.exe the file extracts, but after the extract the installer never runs (I can see the cmd prompt window flash briefly). In %TEMP%, I found the SQLsetup.log with this error:
01/27/2012 15:34:51.059 ======================================================================
01/27/2012 15:34:51.059 Setup launched
01/27/2012 15:34:51.059 Attempting to determine media source
01/27/2012 15:34:51.059 Media source value not specified on command line argument.
01/27/2012 15:34:51.075 Setup is launched from media directly so default the value to the current folder.
01/27/2012 15:34:51.106 Media source: c:\5221130223cc01b446a08e\
01/27/2012 15:34:51.106 Attempt to determine media layout based on file 'c:\5221130223cc01b446a08e\mediainfo.xml'.
01/27/2012 15:34:51.122 Media layout is detected as: Core
01/27/2012 15:34:51.122 Not a slip stream media, so continuing to run setu ...
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