Any ATX power supply with an ATX board will work.

What about with a microATX board?

microATX was explicitly designed to be backward-compatible
with ATX. The mounting points of microATX motherboards are a subset of
those used on full-size ATX boards, and the I/O panel is identical.
Thus, microATX motherboards can be used in full-size ATX cases.
Furthermore, most microATX motherboards generally use the same power
connectors as ATX motherboards, thus permitting the use of full-size ATX power supplies with microATX boards.

That's from wiki.....

So I'm looking for a power supply with a 24pin connection (or 20+4 pin), a 12v rail connector, and on some I am seeing a connection for PCIe connection?

Something like this one at NewEgg.

I have a Rosewill Stallion Series RD500-2SB - 500-Watt ATX12V v2.2 Power Supply powering my GIGABYTE GA-78LMT-USB3.

I'm not saying that helps you, just pointing to one that's worked well for me.

I think that would work. It's at the high end of my budget though.
I am trying to make sure the power supply I get has the connectors I need.
My motherboard has one 24 pin, one 4 pin; I need at least 2 Sata connections, and I will be putting a PCIex16 video card in the computer.

An ATX power supply provides a number of peripheral power connectors and (in modern systems) two connectors for the motherboard: a 4-pin auxiliary connector providing additional power to the CPU and a main 24-pin power supply connector, an extension of the original 20-pin version. 20-pin MOLEX 39-29-9202 at the motherboard. 20-pin MOLEX 39-01-2200 at the cable.

http://en.wikipedia.org/wiki/ATX#Power_supply

Take a look at this article for a little clarification :
ATX12V vs. ATX Power Supplies

There is also the "80-plus" color rating system which has to do with power efficiency.

"80-plus" - Wikipedia

Finally there are PSU calculators to figure out how much capacity you need, e.g. :

eXtreme Power Supply Calculator Lite

or for a simpler one :

Power Supply Calculator - Coolermaster

You'd be surprised at how little you can get away with - Basic machines don't need anything over 300 - 400watts usually.

Enermax makes pretty high quality PSUs and there's a sale on their "Gold" rated PSUs at Newegg right now, until the 15th I think (check the rebate form). I just bought one for a new build.

Enermax gold PSUs at Newegg

Btw, Rosewill is Newegg's house brand - usually pretty good quality in my experience.

Wow, that is the information I need.
According to that second power supply calculator I need a minimum of 290 watts. The power supply I have now is 350 watts. I was thinking I need at least a 450-500 watt PS.

Thank you for all the great info.

Pooh Bear

Pooh Bear,

I could recommend a 500w Minimum for any computer. I would also recommend buying a Good Brand Name. The No Name PSU can Fry your computer when they die. I've seen this happen! Cheap Power Supply fried 2 Hard Drives and a Motherboard on a friends computer (at his home) I had just sat down to look at the computer to see why it wasn't running right (he already had the computer running when I got there). All of the sudden the Power Supply just started smoking, I couldn't get it plug pulled quick enough. Anyway, enough of this story, just be careful installing a cheap PSU!

I just checked mine, it says 629w is Recommended. I'm lucky, I purchased a Beast at 1050w. I purchased an Enermax Revolution 85+ 1050w Power Supply Unit. It should be plenty of power for when I build my next Computer too!

I have been wondering what are some brand names. And what to avoid.
My budget for this is under $50. Or now that I know I can wait a bit and keep using the PS I have, my budget might increase in the future.

Some of the better known brands of better PSUs are :

Corsair, Seasonic, Antec, Enermax, XFX, Firepower Technology (which acquired OCZ & PC Power & Cooling).

I'd always assumed Thermaltake was good, but not sure - I've only bought one of them, and an Enermax and a Seasonic.

Here's another good article :
How to pick the best PC power supply

Any of these Power Supply Units would be okay for your build. They're all pretty much under your $50 Budget, before and after their Rebates. They also have an 80 Plus Bronze rating. Myself, I think I'd go with the Corsair.

Corsair CX Series $49.99 - $20 Rebate Card = $29.99

EVGA $44.99 - $10 Rebate Card = $34.99

Thermaltake $49.99 - $10 Rebate Card = $39.99

SeaSonic $49.99 + $3.99 = $53.98

A couple more :

Enermax 430w (80plus GOLD) $40 after rebate

Enermax 530w (80plus GOLD) $50 after rebate

Okay, I missed those kbarb, I like them both but I'm a firm believer in PSU's 500w or more! Guess if it were me now I'd choose the Enermax 530w for $49.99 after the $35 Rebate Card. I like it because of the Modular Cabling. My last 3 PSU's have been Modular Cabling, Antec, Thermaltake and Enermax.

I pretty much size mine using PSU calculators, plus a little extra. There's no real benefit in getting or paying for a lot more than needed, although they don't actually cost much more now, so it's a bit of a moot point.

Saw a Receipt for my Enermax the other day. I paid around $385 for it! It was a Top of the Line PSU when I purchased it. Knew I wasn't going to be building another computer soon and wanted the Best I could afford on everything! I'm an AMD Junkie so I purchased a Top of the Line AMD Processor, Top of the Line Motherboard, Top of the Line Video Card and a Top of the Line PSU. The computer is not so Top of the Line now, 6 yrs. later, but it will still hold it's own. It sports a 3.0GHz Quad Core Processor, 8GB RAM, 1050w PSU and 2.5TB Hard Drive space 7200rpm.