Try starting IE when you're not online. (IE won't be able to load the MSN homepage, so you should just get a 'page not available' message).
From there, try changing your homepage to 'blank'. Close IE, reboot your computer and connect to the internet. Then start IE. With a bit of luck, it will now open as 'blank' and permit you to change to whatever you want by going to your chosen page and selecting 'Use current' as your new homepage.
I've no idea why that should work but I've managed to fix similar problems on friends' PCs by doing it!
Far better, though, would be to get a decent browser. Based on previous posts, I'd estimate that well over 80% of the regular contributors to AB's I&T section use Firefox:
http://www.mozilla.com/
Chris