There's probably been a lot of these over the holidays but anyway i'm starting to despair!
Just built a new computer and it wont start.
Both mobo (4 and 24) are connected to PSU. CPU fan is plugged in. Mobo is mounted correctly on standoffs. Power and HDD connectors are plugged into Mobo from the case. There is a faint blue light on the case behind the power switch. PSU is switched on and plugged in.
Is it not powering on at all, or is it powering on and not passing the post?
If it's not powering on at all you can check if the power supply is working at all by connecting the green wire on the 24 pin atx connector to a black wire with a paper clip.