Ok i think I need a new power supply but there is one problem are all the power supplies that same size?
I currently have a eMahcines microATX case with a 250watt powersupply, i wanted to upgrade it to a 300 watt or 350watt powersupply but I am not sure if it will fit in my case, because all the powersupplies I have seen are in an ATX form, what should I do without buying a new case? Im saving that as a last resort.

A good sign of a good power supply is the weight; the more the better, thus in many cases making the size larger. The weight is directly related to the quantity, quality, and size of the material used to build it.

Here are some dimensions about power supplies for different forms (ATX, Mini-ATX) that I found through some research that may help:

The following information was obtained from: http://www.directron.com/psu.html

ATX: 6x3.5x5.5", HxWxD. Most common. Uses 4 mounting screws.
Mini-ATX: 5x3.5x5", HxWxD. Rare size. Uses 4 mounting screws. Can be used in a regular ATX case, but often not the other way around.
MicroATX: 5x3x4", HxWxD. Use 3 mounting screws. Not interchangeable with ATX or miniATX.
Flex ATX: Even smaller than Micro ATX. Various sizes according to case specs; often not interchangeable.

so basicly no?

The answer to your question about same size power supplies is - different forms (ATX, Mini-ATX, etc) are different sizes, but as I understand it, each form as a set dimension standard for that form. Hence the listing of different sizes for each form ;-)

The easiest way to resolve the issue would be to take measurements of the power supply, or read them if available on the power supply itself, and simply find a new power Micro-ATX power supply with the same dimensions. Or buy a new case with a power supply. Full ATX will probably be better for your needs if you are considering any serious upgrades.

Not all micro atx cases take smaller dimension power supplies,but i do believe your does .you would be better off buying a full size atx case with power supply,and transfering all you goodies into it !

Lol no way a Full ATX case is way too big for me anyways I contacted eMachines and they said that even a 400watt powersupply should fit in my case.

and with the microATX PS the best one i can find is 250watts and thats what I have now, and is 50watts a big difference or should I go even bigger?

You haven't said why you want to go to a larger power supply, a 300 or 350 should be more than adequate for your power needs. If you need any more that I would be worried about ventlation and go to a larger case.
Good luck which ever way you go
Butch

well if you don't need the bigger and better{runs cooler } case, then you probably don't need the extra power !

What model eMachines do you have? Why would you want to upgrade the powersupply? Are you having problems?

Ok i have the T2245 and my pc restarts on games and my games freeze but I wanted a bigger power supply because Im getting a 3.6GHz P4 HT in a few weeks

and you are going to run that in a micro case !!

y not?
i already have 3 fans in my case

3.6ghz? Not possible..

Also, just to note, if your current PC does not support HT, then odds are your motherboard doesn't. If it doesn't support HT, then it probably doesn't have an 800mhz FSB.

So you will be running at a 533mhz FSB with No HT.

I already upgraded my mobo to a Asus one that supports 533MHz FSB and HT and goes to 2.8+ GHZ

Now I already ordered a new case with a 350watt PS

What I was wondering if the reason because my pc is restarting and running video games so slow and freezing be that I was running a strong video card but I was only running a Celeron processor?
And should a Pentium 4 and a bigger PS fix this?

i tested my memory and its not defected or anything
I reinstalled my OS 2 times and Im still getting the same thing
I ran 2 scan disks and my mobo and video card is brand new, BTW this used to happen with my old mobo (and its onboard graphics so it isnt my new video card) but it only happened once or twice.
So Im guessing it has to be either my CPU or PS

For information about 'freezing':

http://www.daniweb.com/techtalkforums/thread2375.html

Ok, its fairly obvious your doing this upgrade for gaming reasons. It also sounds like you want to go cheap on some hardware, while all out on other hardware, and I understand the motivation, I was there a few weeks ago (as I just got a P2 2.4ghz/800Mhz FSB mobo) and just decided to spend the money on a good case.

A good power supply is critical to your system, especially if your going to be using a P4 of that caliber. If you have a really nice motherboard, then you can get away with a lower power supply. If you bought a cheap motherboard, not possible.

Assuming you want your system to last without 'freezing' from your power supply or lack of cooling, purchase an ATX (not micro) case with an ATX (not micro) power supply. I am going to purchase an ANTEC power supply/case for about $80. I looked at a noname brand for $30 and though. Hmmm.... ok, I could get a noname brand with no cooling, stuff all that hardware into a little box, and have a horrible time cooling the system and keeping the power running properly. I then came to this conclusion after floating around FRY's for a half hour:

If you want a small system for games, buy an Xbox. If you want a PC for games, purchase the appropriate hardware for the job, because you get what you pay for.

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