IE8 keeps forcing Bing on me

Disclaimer up front: this is only on the single workstation at my current client, which definately seems to have some software rot related issues; no other XP or Vista PCs I've ever seen IE8 on has ever shown me this problem. Still... it's very annoying.

Anyway...

Yesterday morning logging into the XP machine I work on took quite a lot of time. It turned out this was because of Internet Explorer 8 being rolled out. I was (and am) happy with that, as generally I quite like IE8.

However, after going through the Welcome To IE8 wizard, I was surprised by the following dialog:

I did not even have Bing as a search provider before. Still, I know this machine to be sort of freaky software-wise, so my initial reaction was "Cool... And even though you apparently added Bing, thanks!" This of course changed when I noticed this:

• In the dialog that opens, I cannot make Google my default search provider; that option simply seems to do nothing.
• Also, I cannot delete the Bing search provider; that option is greyed out.
• Finally, I keep getting this message every time I start IE8.

In essence, IE8 now forces me to use Bing to search, unless I remember to manually change the search provider when I start entering something in the search box. Also it keeps reminding me that it is forcing me to this each time I start IE8. And to top it off, it keeps blaming some other piece software as the reason for this.

If I were inclined to Microsoft bashing, I'd be doing a lot of it right now, I can tell you...

P.S. If you have any ideas on what to do about this, please contribute on Superuser.com.