PSU

300 watts is plenty for what you got.

E7400 65 watt max TDP at stock settings
HD 4670 Full load 64 watts
Motherboard & Ram about another 50 to 75 watts
Hard drives 8-16 watts
DVD burners 25-35 watts
And a Fan or Two 5-10 watts
65+64+75+16+35+10=265watts

So If that sounds like your system you are good to go. If you could though look on the PSU and see how many amps it has on the 12v rail?
 

you would be better off to get a better psu i cant argue with sugestions allready made for better psu's so wont make any of my own