The computer is too powerful, need to slow it down to run Windows PE 2.x.
http://support.microsoft.com/kb/953700 is one of the more interesting KB articles I've read in a while. It describes a problem where some server-class machines with multiple CPUs and certain Broadcom network adapters and firmware suffer from slow network performance. The workaround: Force Windows PE 2.x to run on only one CPU and to ignore all the others. If you've seen this, check out the KB article.