The best you can do is tell him the truth.
His PSU is not up to powering his system.
It may work for now, it may work for the next 6 months but it will eventually fail.
When it does, most low quality PSU's, such as his, have a high probability of surging voltage and frying other components.
It is only a matter of time until it fails.
Tell him he needs to get a QUALITY 500w+ PSU to protect his investment.
Make sure he gets one from Corsair, PCP&C, Seasonic, Enermax or the Antec Earthwatts line.
Normally, you can locate one of the above PSU's in 500w+ form for under $50 after instant/mail in rebates.