L300 just started saying invalid licence

Toshiba L300 laptop was working fine on vista home premium but just started saying invalid licence. Once booted & logged in it gives 3 options

1 access computer with reduced functionality

2 type a different product key

3 contact Microsoft

Tried a few keys but says something about bios not having the key

Ideally, I just want a key that works as the sticker on bottom of laptop is worn blank.

Failing that I'm open to suggestions, hopefully not involving formatting & re installing Windows


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Try getting into bios and set defaults ( start the laptop and pressing F2 and then loading the BIOS setup defaults by pressing the F9 key) also time and date if thats wrong

Tried the advice but still the same. Think I need a working key & then run a windows patch . Think its thst or re install windowd again

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just install Win 7 run daz loader sorted