I'm currently using Windows 7 Home Premium.
Could this have been caused by a virus? Or cleaning up after one? A few days ago, I had something pop up that said a virus had been detected, then it asked if I wanted to quarantine it. I clicked yes. Ater that, the 'Open With' pop up began.
It could have been a faked notice wrapper if you saw it on a webpage, though that was supposed to have been stopped with Windows Vista (and 7). Alternately if it was MSE that told you, it could have been a smaller part of a more serious infection.
In your Star Orb -> All Programs -> Accessories somewhere (I think in System Tools), there should be an Internet Explorer version titled "Internet Explorer (no add ons)" - try running that and see what that does.
Alternately, or in combination, boot into safe mode
and try there.
Can also try
Control Panel -> Internet Options -> Advanced -> Reset to default settings, which might clear the 'always open with' option you may have stuck on. I'm pretty sure there's a way to clear it, though. Would have to look up.