Pidgin v2.0(.1) provides no easy way to change the key bindings (this is intentional) so you can use [Ctrl]-[Enter] to send your message rather than just [Enter] to send a message. This is a problem for me as I usually like to make my sent messages intentional rather than typing something I’ll regret and fat-fingering the [Enter] key.
Since I use the portable version of Pidgin the file to edit is: X:\PortableApps\PidginPortable\Data\settings\.purple\gtkrc-2.0
Its contents should be the following:
binding "pidgin-bindings"
{
# enter inserts a newline
bind "Return" { "insert-at-cursor" ("\n") }
# ctrl-Enter sends message
bind "<ctrl>Return" { "message_send" () }
}
widget "*pidgin_conv_entry" binding "pidgin-bindings"
UPDATE: You might also consider installing my Pidgin smiley theme: http://blog.ozmonet.com/2007/forumsmileys-v08-released-for-pidgingaim/

Justin J. Novack
August 1st, 2007 at 7:30 pm
Note: for Windows, the directory is “
C:\Documents and Settings\username\Application Data\.purple\“and you have to create the
gtkrc-2.0file (just copy yours)February 15th, 2008 at 5:50 pm
gtkrc-2.0 file has to be in Unix format (only LFs at end of lines, not CRLF as in Windows). You can edit it in ie. UltraEdit32 and convert DOS to UNIX befor saving into .purple dir.
March 13th, 2008 at 4:02 am
gtkrc-2.0 with CRLF(\r\n) works under Windows. So it may be in “Windows format”.
(Pidgin 2.3.1)
August 30th, 2008 at 2:06 pm
Note2: and for Windows Vista, the directory is “C:\Users\username\AppData\Roaming\.purple”
May 14th, 2009 at 4:36 am
How do I make it “double enter” = send message, rather than “ctrl+enter” ?
May 19th, 2009 at 11:34 am
Note3: for Windows 7, the directory is “C:\Users\username\.gtkrc-2.0”
April 2nd, 2010 at 4:20 am
Thank you people! Great help.
January 3rd, 2012 at 3:57 am
Thank you! Very helpful!