I removed your HJT log. Such are malware tools and are not permitted in the XP forum and should be posted (in the appropriate malware forum) only when asked for by the BC Malware Team or a malware problem is suspected with cause.
System manufacturer and model, please?
FWIW: SP3 can be installed from the desktop...Windows Update is not the only method. But...before installing it or attempting such...tell us what your system is.
Windows Update problems are routine.
Windows Update Problems, Delete Software Redistribution Folder - http://support.microsoft.com/kb/822798
PC Hell How to Fix Problem When Windows Updates Download But Won't Install - http://www.pchell.com/support/windows_upda...t_install.shtml
Windows and Microsoft Update Problem Solver - http://aumha.net/viewtopic.php?f=62&t=...662971d5dd46450