32 bit:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_BROWSER_EMULATION
Value Key: yourapplication.exe
64 bit:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Internet Explorer\MAIN\FeatureControl\FEATURE_BROWSER_EMULATION
Value Key: yourapplication.exe
http://msdn.microsoft.com/en-us/library/ee330730%28v=vs.85%29.aspx#browser_emulation
The value to set this key to is (taken from MSDN here) as decimal values:
0x2710
ie 10
9999 (0x270F)
Internet Explorer 9. Webpages are displayed in IE9 Standards mode, regardless of the !DOCTYPE directive.
9000 (0x2328)
Internet Explorer 9. Webpages containing standards-based !DOCTYPE directives are displayed in IE9 mode.
8888 (0x22B8)
Webpages are displayed in IE8 Standards mode, regardless of the !DOCTYPE directive.
8000 (0x1F40)
Webpages containing standards-based !DOCTYPE directives are displayed in IE8 mode.
7000 (0x1B58)
Webpages containing standards-based !DOCTYPE directives are displayed in IE7 Standards mode.