LED error code problem.

Hi all, this is my first post here so be gentle. ^_^

I have been fixing PC's and laptops for a few years quite succesfully but this is winning so need a Dell tech for help.

The laptop in question is;

Dell Inspiron 1501

Model number:- PP23LA

Service tag:- <ADMIN NOTE: Service tag removed per privacy policy>

It's way out of warranty so the chap asked what I could do with it as money is tight. The LED error code is solid Caps lock and flashing Scroll lock which I can find no info on and I can't believe no one in the Google universe has come across. The power is OK, the fan is OK, the modem is OK, the Wi-Fi card is OK. I've swapped out the RAM modules and the HDD. I've changed the button cell for the BIOS. I've done a complete strip-down and clean. I've reapplied TIM to the CPU and a new thermal pad to the GPU(onboard). I've done the power reset thingy(?). I've hooked the lappy to a external monitor and keyboard with no joy.

Any one out there KNOW what this error code is for please?

Thanks,

Jusyn.