I was a little surprised this morning to see Windows Vista offer me this optional driver update via Windows Update:

I don’t have a touch screen on this particular machine, so I was immediately suspicious. Sure enough, a bit of searching turns up plenty of reports (like this one at DSL Reports) from people who installed the driver without thinking, to then discover that their existing PS/2 mouse or notebook touchpad stopped functioning. The phantom update appears to be afflicting both XP and Vista systems.
If you install this inadvertently and find yourself with a nonfunctional mouse, the obvious solution is to use System Restore to roll back to the point before the driver was installed. However, at least one report I read online says this option doesn’t work. I haven’t tested so can’t say for sure whether this is true. Another option, which reportedly does work on Vista, is the Roll Back Driver option. From Device Manager, select the defective device (probably under the Human Interface Devices category), right-click and choose Properties, click the Driver tab, and then click Roll Back Driver.
As an alternative, you can uninstall the driver from Device Manager. If you have a USB mouse, plug it in and use it to navigate through Device Manager. If you don’t have a USB mouse to use, you’ll have to do all this with the keyboard, as follows:
1. Press the Windows logo key to open the Start menu and then type device.
2. Use the Down arrow key if necessary to select Device Manager from the search results list and press Enter.
3. If you see a UAC prompt, press the Left arrow key to move the focus to the Continue button, and then press Enter.
4. Press Tab to move the focus into the device list. Use the Down arrow key to move to the Human Interface Devices category, press the Right arrow key to expand that category, and then use the Down arrow key to select the IdeaCom device.
5. Press Enter to open the shortcut menu for this device (or use Shift+F10, is the universal keyboard shortcut that simulates a right-click, and then use the arrow keys to select Properties from the menu and press Enter).
6. From the Device dialog box, press Ctrl+Tab to move through the tabs until the Driver tab is visible.
7. Note that the R is underlined on the Roll Back Driver button text, indicating that it is an accelerator key. Press Alt+R to begin the driver rollback.
If you actually have an IdeaCom touch screen, of course, this advice doesn’t apply.