Wow, that's one of the more bizarre reasons for a system crash I've seen.
I've tracked the offending font down: it's "Mathematica5", as evidenced by it causing both MS Word and Mathematica 7 (which I just installed before the weekend started) to crash. It's a bit strange for that to be the bad font because I don't see any obvious interactions between it and Firefox / Wordpad.
Now I'll see if I can shunt over into safe mode and replace that font. In the mean time, more minidumps for you to look at (with all flags set on the verifier) to see if there's any more helpful details.
Attachment: Attachment 35639