Well first off, the 250 runs cold out-of-the-box, unless you got a faulty card. The 250's overclocking threshold is not really that much to brag about, you might get a 10-15% bump in performance.... As far as folding goes, you can fold just fine with the stock cooler =)
The only reason you would want to WC your GPU would be due to noise or heat issues when it comes to the 250.
To answer your question, it seems that it is not compatible with the 250 if we go by what the website says...http://www.swiftnets.com/products/mcw60-R.asp
But you can always call their tech dept and verify =)