dell inspiron just quit running. and did nothing at all. i checked the power supply and fount that there was no 12 v power anywhere. replaced it with a new 300w unit and all the voltages are present but nothing hsppends...nothing at all

Look to see if there is a fuse.If so it may need replacing.

Contact manufacturer. Their repair people will be able to help you the best.

Look at the motherboard, check the capacitors. If the tops of them are bubbled up or there's something leaking from them, the motherboard is bad. Also, try removing your video card, and running with on board video.

Also, current PC's may need 350 watt powersupply. Check the model of your PC on the dell website to determine the best power supply.

dell inspiron just quit running. and did nothing at all. i checked the power supply and fount that there was no 12 v power anywhere. replaced it with a new 300w unit and all the voltages are present but nothing hsppends...nothing at all

Try reseating CPU and RAM.
Also unplug the power cord, and pressing down the power button over 20 seconds to discharge the PC.

Hope this helps!
Bill
tech manager