I have a burned out Bestec ATX-250-12z power supply for a hp pavilion a320n. I need to know if a Dynex® - 400-Watt ATX CPU Power Supply, will work in its place.

Yes it should do provided your current psu is not a small mATX one. ATX power supplies are pretty generic. Make sure you get one that has enough connectors to suit your system, having said that, Considering it's an off the shelf PC I would guess most PSU's would have the right number and type of connections.

Hello there:
That is a pretty good choice for a replacement you just have to make sure that it will fit exactly like the old one did and that the cables are exact and have the same hookups as the old ones do ok but you should be fine from there ok
Hope this is very helpful for you
Best regards michael

I have replaced this exact model psu for a friend of mine. Symptoms were: false starts, no starts, successful power-ups but would shut down intermittently. The LED on the back side of the unit stayed constantly lit (green). I believe this unit is underpowered... The HP is running a Pentium processor with 4GB of ram. Kinda hard to believe that it is underpowered but there it is.

I replaced the unit with a Hercules 450W switching psu that I have been using for about 3 years now and pulled from another system. Paid $10 for it on ebay and is the best damn psu I've ever owned -- go figure! Bestec is ****. I've seen worse but this takes the cake.