WinXP SP1 hasn't been supported since October 2006.
You've got a VERY bad hijackware infection, primarily because the machine
has been patch in well over eight (8) years. You cannot use Windows Update
unless WinXP SP2 or SP3 is installed so you can't get the machine fully
patched in its current state.
PS: Most antivirus applications will not work properly unless WinXP SP2 or
SP3 is installed.
The only & most efficient way to resolve your problem is to format &
reinstall Windows. After doing so, you'll have the equivalent of a "new
computer" so see...
5 steps to help protect your new computer before you go online
http://www.microsoft.com/protect/computer/advanced/xppc.mspx
Steps To Help Prevent Spyware
http://www.microsoft.com/protect/computer/spyware/prevent.mspx