Blizzard can check any file on your computer.
They have the right to do that when you agree to the terms of use. ( last I checked)
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Changeing the D3Pref's is something I have Known for a long time, I am glad somebody found the motivation to make a Guide, thank you for your work

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I would assume that there would be no Server Warden Detection/Ban issues, But just to play on the safe side, I'll open a ticket to blizzard and ask.
Will Submit the answer (when they reply).
Diablo 3 - My technical issue is not listed here. (Ticket US###########)
Status: Answered
C:\Users\****\Documents\Diablo III
D3Prefs
To make this simple.
I would like to Edit this file, so that I may Run my game in 16 bit mode, and to make the window screen size smaller.
Benefit : Better Performance
Question : If I edit this file, Would / Could I get banned?
I know most of these things are Changeable in game already.
But i noticed the Screen size, and the 16 bit mode are not, wanted to Edit this file and change manually but worried about the possibility of getting banned.
so I just wanted to ask ahead of time to be safe.
#1
12/22/2012 4:06 PM
**** wow worker name
Customer Service Representative
Salutations Name,
Thanks for contacting our Account and Technical support team regarding your Battle.net account.
Our Terms of Use are very clear - use of any third party programs to interfere, read, or intercept any game data from D3 is not allowed and may get your account banned.
If you have any further questions or concerns about this issue, please select "I still have a problem" to provide us additional information. Thank you very much for contacting us - I hope you continue to enjoy your experiences with Blizzard Entertainment!
As a reminder, our number is 1-800-592-5499. Players in Australia and Singapore should call 1-800-041-378 and 800-2549927 respectively if unable to connect via the first number. Live representatives are available between 10:00AM and 6:00PM Pacific Time, 7 days a week.
Elune's Light on you,
Account & Technical Services Rep Siathello
Customer Services
Blizzard Entertainment
www.blizzard.com/support
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Notepad = 3'ed party program.
If you Edit
D3Prefs
You can get banned.
also, if your Right your diablo 3.exe and click properties and compatibility, and disable theme or run in the 640x480 Resolution, you can get banned for that too.
256 colors mode ect.
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Thats what blizzard is telling me.
So if you make Modifications, use at your own Risk.