Normally your BIOS RAM never shut down when you turn off your pc. It stores vital information for hardware boot-up and time synchronization. The BIOS RAM is provided with CMOS battery which keeps it always power on.
Unlink ROM, BIOS RAM is a volatile memory (just like normal RAM). It means, data will go away if you remove the CMOS battery.
The dust can interpret with CMOS battery and cause your BIOS RAM circuit to turn off.
Thus your bios got corrupted.
If your BIOS circuit get damage. Their is no other simple option then to install fleshed motherboard. If the BIOS circuit is good then you can simply update BIOS of your PC manufacture.
Read more answers: http://www.euask.com/topic/6569-Can-dust-damage-your-PC
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