My new PC which i have custom built is not booting with the case side on, i have checked that the case is not trapping anything and it isnt. I have not got the case light connected and it still only boots with the side off. I have decided that the only possible thing must be cooling but the air from the heatsink is cool and when i open the case there is no noticeable heat. This started happening around 40mins ago. Any advice is very gratefully recieved.