Recently I ran into a gentleman who was having several OS issues right after a reinstall. Upon discussion, I found out that the portable system had been connected to his business network for the entire process, and I mentioned that this was probably where the problems came from. The cust seemed to think that was impossible, as apparantly he'd done it like that several times before.
Personally, if he's actually done it successfully in the past, I think it was just luck that he didn't have issues. But for my information, plus I couldn't intelligently back up my claim in our discussion, what types of issues could occur if one is attached to a network whire reinstalling Win2k, or any version of windows really.