I have the belief that Internet Explorer 9 unable to run on Windows XP is really marketing. But I want to ask you if there really is a technical reason why Microsoft didn't release Internet Explorer 9 on Windows XP?
15Probably because mainstream support for XP was discontinued in April 2010.– HydaralMar 17, 2011 at 1:24
Damn. That means I have to buy a new operating system just so I can carry on testing my web pages in all the IE versions.– Matt GibsonMar 17, 2011 at 11:01
2@MattGibson I'm trying to convince my boss to buy me a new computer because of this :-)– PatrickMar 17, 2011 at 12:29
1@Matt: “I have to buy a new operating system just so I can carry on testing my web pages in all the IE versions.” — I understand the frustration, but “just”? How much does Windows 7 cost, and how much money do you earn from making web pages? I suspect it’s worth it. Also note that Microsoft provides Virtual PC images of Windows XP with IE 6/7/8 installed on them for testing purposes. This run in Virtual PC (which is free) on Windows 7 Professional, and VMWare on Mac OS X.– Paul D. WaiteMar 17, 2011 at 15:50
2@Paul I earn very little from web design; that's a spare-time hobby/learning exercise more than anything else; my paid day gig is data warehousing. In my case, in fact, it's probably not worth it until the next paying job comes along. I'll look into those VM images, though, thanks for the pointer! At the moment I'm using VirtualBox with IETester which meets my minimal requirements. I guess I find the thought of an upgrade extra-annoying because I only use Windows for about an hour every month, at home...– Matt GibsonMar 17, 2011 at 16:02
Internet Explorer 9 makes use of two features available in Windows Vista and Windows 7, Direct2D and DirectWrite to speed up the user experience and they are unavailable in Windows XP. There are some minor security features that rely on the newer OS's security models and also make it incompatible with Windows XP.
Get the full down low at Ars Technica - The most modern browser there is: Internet Explorer 9 reviewed.
14@ChrisF I think Microsoft is starting a determined push to get people to stop using their outdated software. Between writing some of their newer software only for Vista/7 to actually encouraging people to stop using Internet Explorer 6 they are getting serious.– PatrickMar 16, 2011 at 17:51
1Also, microsoft stands to benefit by releasing a newer browser on their newer operating systems, as users who are interested in the security benefits will need to upgrade operating systems, leading directly to sales of microsoft products.– zzzzBovMar 16, 2011 at 20:09
6@zzzzBov true, but many of the programs today that run on top of Unix or Linux would not run on the earlier versions of their respective OS. And even though XP SP3 came out just a few years ago, the underpinnings of the operating system are 10 years old. Imagine trying to run the latest software on Ubuntu 4.10, which btw, Canonical stopped supporting in 2006.– PatrickMar 16, 2011 at 20:42
2@Patrick, I don’t see how D3D/DW have any bearing since many people run Windows 7 on a video card that does not support DX10, so they are still unavailable anyway. Besides, acceleration isn’t really a technical reason since without it, pages could still run albeit slower (read the same speed as they have for the last 20 years).– SynetechMar 16, 2011 at 22:49
2And the pinning thingy is not possible in XP. Mar 17, 2011 at 8:53
Well, they could have written Internet Explorer 9 to work on Windows XP. Part of the reason is to move people away from Windows XP, but that's not JUST marketing, Windows XP really is outdated and full of security flaws. It's in everyone's best interest to ditch it, not just Microsoft and hardware vendors...
MS, like many software companies, don't make decisions purely on technical bases. This decision, more than likely, was based on the costs of continuing support on older platforms, and the loss of sales of newer platforms. XP is ingrained in millions of desktop PCs sitting in offices and any small additional excuse to get these corporate IT behemoths to upgrade their Windows licenses is going to be a strategic move for MS.
Ars Technica - Why Microsoft did the right thing in ditching Windows XP for Internet Explorer
The above article goes into more detail, there is shown that it also turns out that Firefox does support Direct2D & DirectWrite on Windows Vista & 7 but on Windows XP it falls back to software mode. But I wouldn't blame Microsoft for not writing this functionality into Internet Explorer 9...
The outdated kernel of Windows XP doesn't include new features that Internet Explorer 9 needs to function, such as Direct2D and a few others (mentioned in answers elsewhere).
However,they were able to work around it, but dude seriously, Windows XP now needs 3 more years to be teenager!