Inspiron N5010 Odd keyboard issue

Had a customer with an odd keyboard issue, I am a field service tech servicing dell products.

the service call was to replace a laptop keyboard, the symptom was laptop makes odd noise and keys dont work.

upom arriving on site the customer was using the laptop VIA the on screen keyboard from accessories, accessability. she could use the onscreen keys with her mouse to select keys, but the laptop was making the keyboard buffer overflow noise it you used any keyboard keys and nothing would type on screen with the normal keyboard. so after assesing the situation I used the USB service key to test the hardware, the only bad results were the battery was reaching the end of life,  I replaced the keyboard with the one that the phone support had sent me out to do.

This resulted in no change,  so I  ran the boot key again, also no problem detected, I rebooted a 3rd time and this time insted of selection of test utility I selected boot to dos utilitys  this gave me a dos prompt and now I can use the keyboard to type normaly, I was expecting that the cursor would race across the screen as if a key was stuck but this did not occure.

Ah hah! so it is not a hardware problem as it only exists in windows, I ran the customers antivirus none were detected. I explained the situation to the customer and what steps I had taken and why this will require a OS reload.

My question, Does anyone have any other ideas how to fix without an OS reload? CU had done a restore point roll back and that did not fix before my first arrival, and windows did not detect any driver errors.