user4823: Using my existing hardware, I want to work out which altcoin is still profitable to mine.
I have found this link:
http://dustcoin.com/mining
But don't know which values to enter into the boxes at the bottom of that page.

How do I work out the SHA-256 and scrypt hashrate
For the Power(W) box, do I enter in my computers PSU wattage? I think it's 650w
For the Power Cost ($/kWh) box, do I check my electricity bill to find out how much I am paying per kWh?


user2343: 
How do I work out the SHA-256 and scrypt hashrate

You can look up your hardware e.g. here (BTC) and here (LTC). But I think it's much easier and more accurate to just try mining different coins for couple hours and measure hashrate directly.

For the Power(W) box, do I enter in my computers PSU wattage? I think it's 650w

PSU wattage is max. power it can supply, so it poses upper bound on PCs consumption. 
To get accurate measurements, you can use something like Kill-a-Watt. Or you can look up TDP of individual components: CPU's, GPU's and ASIS's power consumption is usually listed in their specs, and motherboard+RAM+HDD together usually use around 50W.

For the Power Cost ($/kWh) box, do I check my electricity bill to find out how much I am paying per kWh?

Yes.

4823: <p>Using my existing hardware, I want to work out which altcoin is still profitable to mine.</p>

<p>I have found this link:</p>

<p><a href="http://dustcoin.com/mining" rel="nofollow">http://dustcoin.com/mining</a></p>

<p>But don't know which values to enter into the boxes at the bottom of that page.</p>

<ol>
<li>How do I work out the SHA-256 and scrypt hashrate</li>
<li>For the Power(W) box, do I enter in my computers PSU wattage? I think it's 650w</li>
<li>For the Power Cost ($/kWh) box, do I check my electricity bill to find out how much I am paying per kWh?</li>
</ol>
 2343: <blockquote>
  <p>How do I work out the SHA-256 and scrypt hashrate</p>
</blockquote>

<p>You can look up your hardware e.g. <a href="https://en.bitcoin.it/wiki/Mining_hardware_comparison" rel="nofollow">here (BTC)</a> and <a href="https://litecoin.info/Mining_hardware_comparison" rel="nofollow">here (LTC)</a>. But I think it's much easier and more accurate to just try mining different coins for couple hours and measure hashrate directly.</p>

<blockquote>
  <p>For the Power(W) box, do I enter in my computers PSU wattage? I think it's 650w</p>
</blockquote>

<p>PSU wattage is max. power it can supply, so it poses upper bound on PCs consumption. 
To get accurate measurements, you can use something like <a href="http://rads.stackoverflow.com/amzn/click/B001JHGY2Q" rel="nofollow">Kill-a-Watt</a>. Or you can look up TDP of individual components: CPU's, GPU's and ASIS's power consumption is usually listed in their specs, and motherboard+RAM+HDD together usually use around 50W.</p>

<blockquote>
  <p>For the Power Cost ($/kWh) box, do I check my electricity bill to find out how much I am paying per kWh?</p>
</blockquote>

<p>Yes.</p>
