Is you computer setup to access a network? Is it setup to access a domain?
Authentication is usually a function of network access?
You gave us nothing with which to work. Go to the MS Knowledge Base,
http://tinyurl.com/v1r, from the dropdown list select Windows XP, then type
"XP asks for authentication" in the search box and press enter and see if
any of the articles that come up specify anything similar to your situation.
You do have a legal version of XP don't you? Is this a recent issue or have
you always had this problem. When did the problem appear, can you recall
anything that preceded it that might have set off the problem, had you
recently reinstalled, did XP pre-loaded on your system, if yes, was it built
by a shop or major manufacturer or did you buy XP at retail?
If this is a relatively recent issue, you might use System Restore to take
you back to a time prior to when this began. Start\All
Programs\Accessories|System Tools\System Restore.
