For my sins, I recently got a new PC at work with Vista installed. I've been working on development of a website and have been checking IE7 and Firefox throughout (and Safari on a Mac as well - although still to fix for IE6). However, it turns out IE7 on XP is displaying certain things differently from IE7 on my Vista machine! Obviously conditional comments are the normal way of coping with rendering differences between IE7 and IE6 etc, but how on earth can I ensure that my site looks identical on IE7 XP and IE7 Vista?!

An example of the problem is at the following URL, where the Request Prospectus link is aligned correctly on XP, but on Vista it is way off to the left. My XHTML and CSS validates fine, so I'm not sure what's causing the problem. Any help appreciated!