Hello there, I think the problem is that your Windows XP is still running on service pack 2 so please check it,
if it still running on Windows XP Service pack 2 try upgrading it to Windows XP Service Pack 3, most of the Windows XP problem can be solve by this upgrade,
or it might be your anti virus is preventing the launch of the the InfinityMu client so just turn it off before launching the InfinityMu client or add it to the antivirus list of exception, also try using the mu.exe instead
hope this can solve your problem if not try to update us
