TechBeta

With the release of Windows Vista Beta 2, I want to announce that we will be naming the version of IE7 in Windows Vista ?��Ǩ?�Internet Explorer 7+?��Ǩ��. While all versions of IE7 are built from the same code base, there are some important differences in IE7+, most significantly the addition of Windows Vista-only features like Protected Mode, Parental Controls, and improved Network Diagnostics. These features take advantage of big changes in Windows Vista and weren?��Ǩ�Ѣt practical to bring downlevel. The IE7+ naming gives us an easy way to refer to this version. (?��Ǩ?�The version of IE7 in Vista?��Ǩ�� doesn?��Ǩ�Ѣt roll off the tongue as easily?��Ǩ��)

These differences shouldn?��Ǩ�Ѣt affect most web developers, but if you need to know specifically, you can refer to the OS field of the User-Agent string. As Eric noted previously, the User-Agent strings will have the info you need:
IE7+ running on Windows Vista: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.0)
IE7 running on Windows XP: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1)

Read more: IEBlog