Well for one thing, that particular 500w is some fly-by-nite brand i've never heard of. Also it's cheap cuz it's sub sub-standard equipment. The one i suggested is a name brand company and it's been used by ppl who know quality made and it's reliable. You can go with that one if you like, but before you buy it, ask ppl who have used it. I don't think there's ppl here who have used a "achieve" psu before.
You can also go on newegg and look for other brands of psu's.
Raidmax
Enermax
Allied
These psu's are pretty good too. You can search for a 400w psu with these brands and see what you come up with.
You also have to remember that when you buy something like that on ebay and something goes wrong with it, you can't return it for a repair or a refund. You're kinda stuck with it.
At least with name brand psu from newegg, if it goes bad or malfunctions,send it back and get it repaired, replaced or refunded. That's good that you did research on these parts. I understand this is your dad's money and you have to watch what you spend,but would'nt you want quality name brand parts in your rig? Evrybody likes to save some money,hell i do too but i'd rather spend that extra buck knowing i'm getting quality stuff and i know it will last me and just incase it goes bad, i can always return it for a repair, a replacement or a refund.
Don't let me turn you away from buying what you want, all i'm doin is suggesting what I would buy for my rig. Remember, this is gonna be your gaming machine and i'm sure you would want it to last you a while. Not konk out in 3 months.
Check this one out:
Raidmax DUAL FAN Power supply for P4/K7 Motherboards PM-S400 **AMD approved**Raidmax Dual Fan 400W Power supply Specifications: Dual Fans 1 Front, 1 Back ATX 400W POWER SUPPLY UL, CSA, FCC, CE Approved. Model#: PM-S400 Special FedEx Saver Shipping $6.00
$40.00
http://www.newegg.com/app/Showimage.asp ... 002-03.JPG
This one will do nicely and it's cheaper. Name brand psu
