If you installed XP from CD and then copied the installation discs to your hard drive,use this hack to change the default installation folder that XP will look for when it searches for additional files later.
Type "regedit" in the Run Command and then navigate to :
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\
CurrentVersion\Setup
Change the string value called SourcePath to one specifying the path to where the XP setup files are now stored.This will make XP to look in this new location, instead of you clicking "browse" and browsing to there.
