How can I tell if I have a large enough power supply?

I have a 300W power supply on a system running: 1 Seagate 7200RPM 60 GB Hard Drive
                                                1 DVD-ROM
                                                1 CD-RW
                                                1 Floppy Drive
                                                1 AMD 2400+ processor w/fan
                                                1 ECS K7S5A Pro MoBo
                                                1 system fan in front of case.
                                                1 Blow fan (fits in i/o card slot)
                                              1 MSI GeForce 4 MX 440 AGP 4x 64MB SDRAM Video card w/TV-out
                                              1 USR 56K modem.
I know you probably can't tell from this without the power requirements from each of these products, but I was hoping I could get some idea if 300W would be enough.

I would either like to add another case fan in the rear that would pull the air flow more over the processor. My processor is running at about 46-47 degrees celsius when idle. It seems a little high to me when it is just sitting there doing nothing. Is 300W powerful enough to handle all this and possibly another fan? Does the 46-47 degree idle temp seem high or is that good? Thanks for any input.
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rrhunt28Connect With a Mentor Commented:
46 to 47 is normal.  If your system runs stable, and you do not have any crash problems, especially in heavey cpu usage like playing games, your power supply is probably fine, and if you add more hardware you can aways add a power supply later.  And AMD's do not run hot, they run in the same range as other similer processors.

I think that a 300W power supply would run everthing you have listed, but I highly recommend that you purchase a new 400W power supply.  The temperature you listed is on the high side, but remember that AMD cpu's run hot.  I would not worry about that range of temperatures.
if your curiosity gets to ya.. you can go to this page, and go thru the config to see what your system draws/needs,,30_182_869_1039%5E1053,00.html
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I see no problem with running all that on a 300W PSU.  

The temps are fine, that is about what you can expect an Athlon to run at.  Adding fans will not pull too much more power, it's not like you want to add a DVD-R drive (which uses quite a bit of power).  

Unless you are having system instability problems, then I'd say there's no reason to worry about the power supply at all.
The type and speed of your CPU is a big generator of heat and consumer of power.  Also the memory in your system.  300W is good enough for a typical system like yours, but you would need to list more details for people to really have a realistic idea.

As long as your system is stable and doesn't crash then everything is OK.

If you power supply doesn't have enough power then your system will crash when you try to do something "taxing" like run a complex program or use the CDROM and hard drive at the same time.

Typically the largest power drain is during startup/boot-time.  So if you system boots up it is probably fine.
MillwoodAuthor Commented:
Thanks folks. It seems to be booting up fine and runnning simple standard windows programs and games. I haven't tried anything that would really make it work hard yet.
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