Uninstall the program, if that does not help, do a System Restore and pick a restore point to before you installed this.
If a system restore does not help, boot the PC off the XP disk and do a "repair" of Windows.
If that also does nothing, you'll need to fully re-install Windows or live with the icons being messed up.
I agree with the solution up to the point of reinstalling Windows.
Delete the icon cache, and renew it:
Right-click an empty area on the desktop,
select Properties, then settings.
Change the screen resolution to anything lower than you are now using.
Click Apply, click OK.
Go back and restore your original screen resolution and click Apply and OK.