Kraken92

Greetings everyone. I've been having a strange problem with my desktop lately. When clicking the power button for it to switch on, it either does a single 'click' sound and won't boot, or it boots normally but as soon as I insert my password and get to the windows main screen it automatically shuts off. I'm guessing it's a PSU issue, but can't really be sure. I've tried removing any dust inside and checked if the wires connected to the PSU are loose, and everything seems to be ok. When it won't even boot up, the fans do start spinning for a second I've noticed, if that helps at all. Is there anything I can do/test to try fixing it or do I need to take it to a technician? Thanks in advance! Computer specs: OS: Vista CPU: Intel Quad Core 2.66Ghz Hard Drive: 500 GB RAM: 4 GB Graphics Card: 460 GTX ( I think)