Any of the points mentioned in the preceding posts might cause this, and related to maxinexus's first point...is this possibly a Gateway PC, as they used to have this wonderful ANY KEY 'feature' available for configuring their keyboards, which I once had to research how to disable as it caused exactly the behavior you mention when users accidentally enabled it.
wen typing in a webste such www. all different letters pop up but not the ones that I want
Go to Control Panel/Region and Language/Change Keyboards/Advanced Key Settings
I found a default Hot Key to change between input languages (Left Alt/Shift). It cured my problem immediately, then I cancelled all of the actons.