Probably what happened is that you have a faulty driver install. There are a some ways to try and fix this.
1. You could use boot up into Rescue and Recovery and choose Restore Factory Contents. This will erase all existing data on your C:\ drive and reinstall Windows with all the IBM drivers and software.
2. You could boot up the Product Recovery Discs and Restore Factory Contents. This will erase all partitions and data on your hard drive and reinstall Rescue and Recovery with files to restore your C:\ partition. You will have to choose to Restore Factory Contents again to install Windows with all the IBM drivers and software. Normally you can create these discs yourself from the Access IBM folder or ThinkVantage folder off of Start > All Programs. If you cannot make a set for yourself at this point, you can order them from Lenovo for about $45 US.
3. You could reinstall Windows, make sure to cancel any found hardware wizards, then install the IBM drivers for your T43 following the installation instructions on the download page. You could try
ThinkVantage System Update, but I do not have a lot of faith in it yet. You will need to reboot after installing the drivers.
Drivers and software - ThinkPad T43, T43p
4. You could do a repair install of Windows. See following page for info on this.
Langa Letter: XP's No-Reformat, Nondestructive Total-Rebuild Option
5. You could go to Device Manager and uninstall all suspect devices (right-click on device to uninstall it). Reboot and see if it works. If not, uninstall all suspect devices again, then cancel any found hardware wizards on reboot. Next install the IBM drivers for your T43 then reboot again.