The process.start has a few arguments, you should put the path to the executable in one, then in the arguments argument, you add the other pieces, like:
Process.Start(@"E:\UnInstall\SQLServer\SQLServerExpress2008\SQLEXPR_x64_ENU.exe", "SQ/SAPWD=\"testpwd123\"/security=SQL/BROWSERSVCSTARTUPTYPE=\"Enabled\"/TCPENABLED=\"1\"/NPENABLED=\"0\"/INDICATEPROGRESS=\"True\"/INSTANCENAME=\"CBEInstance\"/IACCEPTSQLSERVERLICENSETERMS=\"True\"");
MSDN Documentation on Process.Start[
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