Logon credentials problem

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Ok, so ive been playin with windows xp mode beta in win 7 and i have one problem. After installing my own version of xp-sp3 i cannon get it to integrate to win7 , when prompted for logon credentials it keeps sayin incorrent username or domain etc..

Now is there suppose to be a difference between the regular logon info and the credentials in which its requiring ?>

Any help will be good !