Might work to install the SW for the video card.

Reboot and disable the integrated graphics...save and exit.

Turn off and UPLUG PC.

Install new card. Replug AC power.

Restart PC....will it run...probably but I wouldn't waste much time getting a higher wattage quality PSU. Always better to have 'reserve power than have too little...450W is where I'd start and don't skimp ...get a good PSU.