Windows Vista: Touchpad behaves erratically. Often while you are typing, the cursor and the prompt will change its position by itself. "Solutions" to "alleviate" the Problem.
Key words: Touchpad issue, Mouse issue, Cursor moves by itself, Cursor is crazy, Cursor moves erratically, Prompt moves by itself, Cursor Focus changes automatically.

SYMPTOMS

You may be typing something in your web mail, in a word document or in your blog and suddenly the prompt moves to a different position on the screen. 

This causes you to type text in other location, erase text, etc. If this happens to you, you know how annoying it is and  if it happens often, it will be a real nightmare.  Many users claim that this problem appeared after Windows Vista Service Pack 1 was installed.  In any case, this problem was not seen in Windows XP.

I am not sure if the prompt actually moves to the same position or if it moves to any random position. But at least in my case, it always seems to move around the same position (always line above of where I was typing something).  This may happen suddenly anytime while typing. 

CAUSES 

A. "Advertised" Cause #1
Some users claim that the problem is due to the user accidentally touching the Touchpad lightly and because the Touchpad is set to be very sensitive, it moves the cursor to a different location on the screen. However moving the cursor is only half of the problem.  The problem is that the cursor moves out of the current position and then it is activated (like you clicked the mouse button, thus activating the prompt into the cursor position). So besides touching the Touchpad, you would also need to click accidentally in one button. Or the problem is like if you would have pressed the arrow keys, but you didn't!

But I think most users are not touching the Touchpad. Simply one of heir hands is resting on the laptop case and is partially over the Touchpad without actually touching it. 

B. "Advertised" Cause #2 Other users claim that the problem is due to a bug or a software issue in Windows Vista SP1 and they are waiting for Microsoft to produce a fix up. 

C. "Unknown" Cause#3 Microsoft states the following: Before you install Windows Vista SP1, you should know that after the installation, occasionally a sound device or some other hardware device may no longer work. If this occurs, just install an updated driver for the device. Here it states "may no longer work", it does not refer to a device acting erratically but in its web page Synaptics suggests the solution or reinstalling the driver if you have an erratic cursor. However, what exactly means "erratic cursor"? Does it refer to the pointer of the mouse moving erratically or to the actual cursor (place to enter text) moving automatically somewhere else than the position you were thinking the cursor was? 

SOLUTIONS 

1. "Advertised" Solution [I don't know how to do this so it did not work at all for me]
It suggests you decrease the sensitivity of the touchpad. Notice that the sensitivity of the touchpad has nothing to do with the speed of motion of the cursor. So instead I decreased the speed at which the mouse pointer moves. This will also decrease the speed with which the pointer will move when you drag your finger across the Touchpad. This solution did work well for me.  

2. "By-Pass" Solution [Alternate partial solution - useful if you wanna use just an external mouse]
Two suggestions are made.
a) Disable the Touchpad at the BIOS configuration. You can do this by booting your machine and accessing the BIOS configuration.
b) Disable the Touchpad in the mouse settings (Control Panel / Mouse / Device Settings  -> Disable). If you can't find this option in your Mouse settings, it is because you don't have the latest driver installed. In my case, my computer didn't have settings for the Touchpad. I downloaded the driver update and the settings menu was updated (http://www.synaptics.com/support/drivers). The icon of the Touchpad will appear on the bottom menu bar of Windows.

This solution works well if you have an external mouse connected. Otherwise you will be left without a pointing device. If you need to switch between Touchpad and no Touchpad, disabling the Touchpad via the BIOS is not useful at all.

So the best way is to disable the Touchpad when you don't need it by using the configuration menu.  This will for sure solve any erratic cursor issue. 

Advice : It may be a good idea to first configure your external mouse to every USB port in your laptop. If you don't, if later you remove the mouse and put in another port, your computer may not recognize it or it may take a long time trying to set the driver. 

3. "Add-on" Solution [works well but read below]
Some suggest that you download and install software that will disable the Touchpad when you have installed an external mouse. Others suggest you download and install software that will disable the Touchpad while you type. I have tried the last one. But it requires you to install a software that will reside on your computers memory (using more resources), also the source of the software is not well known and it is unknown if there are any issues with the software. This "add-on" solution did fix my problem but I had computer problems later (unrelated) that forced me to do a full recovery of the Windows installed in my laptop.  So maybe the medicine could be at the end, worse than the problem. 

4. "Update driver" Solution [decreases the problem significantly but still happens every other time] Synaptics states the following:  

My cursor is behaving erratically. 

There are two possible solutions to this problem: 

1. If your TouchPad is dirty, use a small amount of ammonia-based window cleaner on a clean cloth and gently wipe the surface of the TouchPad to remove any dirt or grime. Having a clean TouchPad surface usually eliminates erratic pointer movement. 

2. The TouchPad driver may need to be updated. Download the appropriate Synaptics driver from the manufacturer's support site. Uninstall the driver that is not working and then install the downloaded driver.

First check if your Touchpad has a driver in the driver CD or the set of drivers that came with your laptop. If not, visit the webpage of your laptop manufacturer and check for driver updates. If you can't find any driver, you can visit the touchpad manufacturer web page.

In my case, my laptop CD didn't have a driver for my Touchpad. After visiting the support webpage of my laptop's manufacturer, I found no driver available. So I visited http://www.synaptics.com/support/drivers and downloaded the driver for my platform (Windows Vista 32-bit Edition). Notice that Synaptics warns you that if you install this generic driver you will lose any special configuration that your laptop manufacturer may have costumized for your laptop. This will be all right for most cases anyways and is certainly okay if your laptop manufacturer does not supply customized drivers for your Touchpad. 

Suggestion and Conclusions

1. Follow the "4. Update-Driver solution" first.  If this doesn't work well for you, then try to reduce the speed of the mouse pointer.

2. If the above doesn't work, try "2. By-Pass solution. This disables the touchpad.

Status on my laptop

Currently I use my laptop with an external mouse and the Touchpad disabled. This has solved my problem.