IE7 Beta 1 is not supposed to work with XP x64. XP x86 SP2 and Vista only. What kind of message does this send to our partners and customers?
"Wait for Beta 2."
"Well we've done what we could and ... oh, ahh, yepp, we should should have thought about 64-bit."
"64-bit?"
"My goal is to build IE7 and 32-bit is the most important platform."
"It works in Vista."

I don't know but all of the above seems wrong to me (And I made it up!). For now I will go and install Vista x64 and see.