Quote - IE8 doesn't work very well on a lot of sites anymore (no HTML 5 support) and it's not very secure (later verions of IE are much more secure). Programs that use the IE WebBrowser control for displaying webpages, which is quite a few, are having the same problems on XP/IE8 systems.

MS will soon not update XP with security updates anymore anyway, basically it's not very secure compared to newer versions anyway so the best thing is to upgrade to Win 7 or 8 which will solve all these problems.

Microsoft backpeddled and exended Windows XP secuity support till 2015.  So IE 8 wil continue to get security updates.

I agree, sites which use custom IE controls are going to have problems, that's not the same thing however as being unable to support HTML 5, because you can easily have fallbacks for most non HTML 5 content.  Apple's website does this with CSS transitions on their main image sometimes, where the fallback for clients without it, is a single static image.

Also, not every current browser fully supports all parts of HTML 5.  So, to have a graceful application, you need to do feature detection, and load only what the client can actually use.  In the case of IE 8, you get square corners instead of rounded ones, but hey, it still works.