just had same problem, look at the header information in the email. I found the email came from the internal network, one of my machines had a virus. In outlook open email view / options look in header info for anything that might help.
i made a boot disk with http://www.nu2.nu/bootdisk/modboot/ works great. I have yet to get the install to work after 2 days of trying. This will get you logged into the domain, map your xp distribution point and get you ready to install. Let me know if you get it to work?