As mentioned before, it could be the power supply. I had a generic 450 w power supply that failed after a year of running my 8800gt. Just put the card in your friends system to make sure it works; if it works it is your power supply.
The E4300 should overclock nicely (at least 2.4 GHz). If you overclock, you can get a 4850 for around $100 or less; if you have more cash get a 5870. If you don't overclock, stick with the 4670.