You cannot type numbers by using the numeric keypad on your keyboard when you turn on the MouseKeys accessibility feature in Windows

When you turn on the MouseKeys accessibility feature in Windows Vista or in Windows XP, you cannot type numbers by using the numeric keypad on your keyboard.

This behavior may occur if you set the MouseKeys accessibility feature to be enabled when the NUM LOCK key is on.

If you use the numeric keypad for data entry, set the MouseKeys accessibility feature to be enabled when the NUM LOCK key is off.

To work around this behavior, use one of the following methods:

• Specify that the NUM LOCK key must be off for the numeric keypad to function as MouseKeys. To do this, follow the appropriate steps.
  
  Windows Vista
  1. Click Start
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     .
  2. In the Start Search box, type Ease of Access.
  3. Click Make the mouse easier to use.
  4. Click Set up Mouse Keys.
  5. Under Other Settings, click Off next to Use MouseKeys when NumLock is.
  6. Click Save.
  Windows XP
  1. Click Start.
  2. Click Run.
  3. In the Open box, type access.cpl, and then click OK.
  4. Click the Mouse tab.
  5. Click Settings.
  6. Next to Use MouseKeys when NumLock is, click Off.
  7. Click OK two times.
• Turn off the MouseKeys accessibility feature. To do this, follow the appropriate steps.
  
  Windows Vista
  1. Click Start
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     .
  2. In the Start Search box, type Ease of Access.
  3. Click Make the mouse easier to use.
  4. Click to clear the Turn on Mouse Keys check box.
  5. Click Save.
  Windows XP
  1. Click Start.
  2. Click Run.
  3. In the Open box, type access.cpl, and then click OK.
  4. Click the Mouse tab.
  5. Click to clear the Use MouseKeys check box.
  6. Click OK.