I want to upgrade my DELL XPS420 with a 375 watt PSU to a dell recomended 500 watt. so that i could go to a better graphics card. But was told that it might harm my motherboard because dell only recomended up to 425 watt Is that possable?
The motherboard will draw the power it needs, you can run a 1kW PSU in a HTPC that only needs 100 watts and it wont have a problem. Dell probably only recommended up to that level because thats what they had cheap discounts on, a higher powered PSU will not cause an issue.