Vista - ISATAP & Teredo prevent Vista from booting to desktop after login

Hello.
Vista Ultimate.
The computer recently stopped booting up all the way. It will boot to the
login screen, but after login, the hard drive just thrashes and the computer
never will boot to the desktop, it just displays "Welcome" on the screen.

Using boot logging, found that it stops at the isatap driver. I removed the
isatap and teredo drivers and the computer will then boot. The problem is,
when this laptop is brought in to the company network, at boot up the drivers
are re-loaded and the computer will not boot to the desktop.

Before this problem started, a program for a pda was loaded. It did not work
properly to appear on the pda. After this the problem started when the
computer is connected to the company network.

The program was uninstalled, system restore was run twice using different
restore points. Problem not corrected.

Network drivers were re-installed from manufacturer's driver CD.

My question is, is there a solution to correct the problem with isatap and
teredo drivers, or is there a way to uninstall and prevent them from
installing again afterward?

Is there a way to restore the original files from the Vista disk besides
installing from scratch?
Don't want to rebuild computer just to repair a driver.

Toshiba U205-S5057 laptop.
Intel Pro/100 VE Network Connection
Intel Pro/Wireless 3945ABG Network connection

Then it has:
isatap.{string of letters & numbers}
isatap.domain.local
Teredo Tunneling Pseudo-Interface

When the isatap and Teredo are gone, the computer will boot. After they
reinstall, it will not boot to desktop. No blue screens, etc, just will not
load anything past the isatap driver and stays at the Welcome screen.

Thanks for your help.

KT