PSU fails if I add in a CDROM and HDD

So I have finally got my rig, tht is to say mobo, cpu and half a gig of memory, to post and all looks fines. However, if I add a HDD in a caddy and/or a DVD RW th PSU flicks on for a fraction of a sec and fails. If I remove them it works fine again. i cant believe this is a power problem because the ROM And HDD are not gonna draw that much power, and this is branded as 650 watts, although I know such branding counts for absolutely nothing much of the time. In particular this acts just like a couple of third rate psus I had before which was linked to low power. Any ideas?

 

Try another PSU, borrow one from a friend, pull one from another PC temporarily, buy a used one somewhere, whatever. It almost has to be a bad PSU, but there is a small chance that the DVD drive is hosed, causing some type of short.....

 

Hey Hopper. Yeah I thought this as well so I ran the dvd drive in another system and it ran fine. Ran just the caddy nothing, think I ran just the dvd too, nothing. Will get a new psu, I seem to get through them by the bucket load for various projects anyway.