I own a 475W HEC PSU - I'm going to buy a new system and I was wondering if I could use it in the new mobo.

The new mobo has 24 pins and the PSU has 20 pins. It will be ashame to throght it away.

I'll say no. Because it has too few amps on the +12 volt rail. Probably less than 20 amps, too low for todays stuff. Best to go to xtreme systems and look up thier PSU sticky on whats good. A tier 2 500 watt +12V 30 amp is usually a good starting point.

What is your new system going to be made of?

Yes. It will work with your new motherboard - the extra 4 pins on the 24pin motherboard connector just supply more of same voltages which are fed in on other parts of the connector ... many people (including myself) have 20 pin power supplies running on a motherboard with a 24pin connector and have never had problems related to it.

However, conumdrum makes a good point ... a quick google search shows your power supply only has 15Amps on the 12v rail (18Amps peak) and that a lot of the peak 475watt it claims is on the 3.3v and 5v channels. Current (good) power supplies having only a single 12v rail will supply 30Amps or more.

Basically ... it depends what components you use as to whether or not your power supply will be able to handle it. If you post what you're going to be using, we'll be able to see if you need a better PSU or not.

My system will be: Core 2 quad 6600, 4 gig mem (DDR2 800), HD 3850, 2XHDD,
I'm not planing overclock. Not planing crosfire.
I thought about enermax 400W liberty if my hec isn't up to the task.

Hmmm ... you could use your old power supply, as long as you understand that if you upgrade any component (or overclock any component) in it to a more power hungry one you're probably going to need a new power supply to go with it.

As it is, you'll be running it fairly heavily which means the power supply may not last as long as it would otherwise.

My advice would be, as long as you can afford it, to get a new power supply. I've seen a couple of computers now where the power supply has died due to age/overload etc. and taken other components with it (hard drive being most annoying to fix, motherboard being most expensive to replace.

As for which power supply, there's a stickied FAQ on this forum you can read for some advice.

I'll buy a new PSU - how many watt would I need for this system?

I'll make the HEC my htpc PSU with my old comp (Athlon xp 2200)

Using the ultimate PSU calculator...
(http://www.extreme.outervision.com/psucalculator.jsp)
Your system will use around 240watts at load ...
Which means you should aim for a 400-500w power supply (as greatest efficiency is at roughly 50% load.

THANKS - I THINK ENERMAX LIBERTY WILL BE MY CHOISE