How to encrypt a section within web.config using aspnet_regiis -pe or -pef

Question

I am a developer trying to encrypt part of my web.config file in an ASP.NET site (first time I've tried this...).

Having repeated failures with all types of syntax changes, so perhaps better to post here. Here is one example of a failure (I copied web.config into c:\temp) from cmd prompt hung off Visual Studio 2010 program tree:

Setting environment for using Microsoft Visual Studio 2010 x86 tools.

C:\Program Files\Microsoft Visual Studio 10.0\VC>aspnet_regiis -pef "applicationSettings/Webclient.Properties.Settings" "c:\temp" Encrypting configuration section... The configuration section 'applicationSettings/Webclient.Properties.Settings' was not found. Failed!

C:\Program Files\Microsoft Visual Studio 10.0\VC>

• Originally, I posed the question in SO here (no real help after 3 days):

http://stackoverflow.com/questions/8481562/aspnet-regiis-pe-cannot-find-my-configuration-section-in-net-v4-0-30319

• Then I posted question here for help:

http://forums.asp.net/t/1748951.aspx/1?How+to+get+ASPNET_REGIIS+to+encrypt+a+section+of+my+web+config+file

• Latest forum where I've sought help:

http://social.microsoft.com/Forums/en-US/partnerdevaspnet/thread/faac591f-498e-461d-970f-c2d8f9a7a4f5/

• Here is the web.config:

12345abcde abcdef12345 http://MDWDATA/sdkTrimFileServiceASMX/FileService.asmx