Starts but no Bios

[cardgunner]

I opened a working computer and removed the memory cards for inspection. I put them back in and now the computer starts but doesn't boot. No bios no nothing. The fans work but that is about it. I didn't have to unplug anything to extract the cards.

Any ideas?

Thanks,
Cardgunner

 

[cardgunner]

No it was turned off and unplugged.