Why doesn't touchpad respond?

SOURCE: touchpad tapping for MSI Wind U100 laptop

Usually this on/off feature comes with the manufacturer drivers. If (I'm assuming you are using windows) the OS was re-installed, it just uses a generic driver which does not include advanced options. And MSI seem to not provide this driver (I've searched). Maybe there is an option for it on their System Control Manager. You can download it here:

http://global.msi.com.tw/index.php?func=downloaddetail&type=utility&maincat_no=135&prod_no=1474

In LINUX, it is a bit more complex, because it is not easy to get a specific driver for the touchpads .

SOURCE: Touchpad Sensitivity

Click on the start menu and select "Control Panel". Once in the control panel, select "Hardware and Sound". Once in the hardware and sound menu, click on "Mouse". Once the mouse menu comes up, there should be a tab labeled "Dell Touchpad". Click on that tab and then click on the large touchpad icon to take you to the touchpad options. Once in the touchpad options menu, click on "Device Select". Once you click on deivce select you should see the option to "enable" or "disable" the touchpad.

SOURCE: my touchpad mouse won't work. it does not respond

If you are using XP, check your mouse settings under Control Panel. Make sure that your Touch Pad is enabled. If it is but it still won't work, have a mouse plugged into a USB port that will work correctly. Then download the latest driver from the Acer site for your touchpad. Uninstall the driver that is currently being used by your system. Then install the updated driver that you downloaded. This should allow you to use your Touch Pad. If not, you may have to take your laptop in for servicing.

SOURCE: touchpad on Packard Bell Easynote not responding

the fn key and one of the f keys should turn this on and off, if not
its possible the cable from the touchpad to the motherboard is loose or the touchpad is bad

SOURCE: Touchpad not responding in netboook

There's a little button right above the touchpad. If the light on this button is orange, the touchpad is disabled. Press it again until the light is white again and your touchpad should work.