Boot up into safe mode and see if your mouse works. If it doesn't, then it is probably defective. If it works, then it would be a configuration issue in the normal side of the o/s.
See if that will help you narrow it down.
If the mouse pad is defective, it may not be worth fixing, just go out and buy a small usb laptop mouse.
Good luck.
-Carlos:
blinking red light on Sony laptop model PCG 9RGM or K215M PC comes on but not progressing to...
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blinking red light on Sony laptop model PCG 9RGM or K215M PC comes on but not progressing to Internet access