Bestec power supply model ATX-300-12Z Rev BD green indicating light flashes on off when plugged in.

Not necessarily. The green light usually just signifies power to the power supply. Amazon sells a cheap power supply tester that can verify everything on a power supply from old to new.

Hi;
you should check the capacitor in the secondry side of the power supply,

all atx powersupplies are generic-it dous not really matter what computer it comes from unless its a high end pc requiring loads of power-if your machine is intel you may need a supply with an extra twelve volt lead(two yellow and two black leads in a little block)-but for that pc i would just harvest a powerpack out of a dead machine

plug your pc directly to your wall outlet and see if it turns on. If it works, then the problem is your power supply. If power supply has a reset button, press it and try again. If pc does not turn on when plugged to wall outlet, then power supply for pc may be out.

Most likely yes.

I would also reccomend an upgrade to that PSU when replacing it.

Something in the 450-Watt neighborhood is usually a bit more robust.

Do yo have a volt meter or an atx psu tester?
you can check voltage to see

If a power supply is bad, your pc will turn off or/and turn on and turn off. As long as your system is running without and shut downs your good.

However if your pc is turing off, I would change it as soon as you can. basically what is happening, when you unplug everything there isn't much of a draw on power so the light remains steady, but when you plug devices in there is a draw and the PSU cannot deliver.

I hope this helps.

Your power supply is fried. I had the same problem with my Bestec ATX 250 power supply. I fixed the problem by installing the StatTech model: ATXPOWER250. It was easy to install and works well. It is almost identical to the original but more quiet. I got it for $29 at MicroCenter.com. Also at online Newegg.com, Radioshack.com, Provantage.com, June 20,2009

Repair shop

I have already replaced mant Bestec ATX-250-12E power supplies because they have an internal failure. Consider yourself lucky if the thing doesn't power up your computer because it has a problem of imposing the +12 volt line onto the +5 Volt line then blowing out the mother board. Sometimes you aren't so lucky because once the damage is done then it is to late to just simply replace that piece of junk. I was lucky with my daughters E-Machine because if she tried pressing the start switch on the front of her computer it would sometimes come on and sometimes not. She just mentioned this to me and I immediately replaced that Bostec ATX-250-12E before it could do any damage to her computer. If anyone has an older E-Machine or an older Gateway machine then it would be a good idea to see if it uses that Bostec-ATX-250- 12E. If it does then go order another power supply, anything but a Bostec, and instead of a 250 watt order a 300 watt or better. I hope that this has helped those that might have this problem before it destroyes *********** boards. Marty

it has a blinking lite whats wrong