Yeah, I think you might need more power.
1. Buy a replacement power supply (But you would need to make sure you get the right size. The most common is ATX but with only 250watts I'm guessing you might have a small computer that might not be ATX. It could be micro ATX or another small case standard of some kind)
2. I think you would be a good candidate for a supplimental power supply. This is a power supply that fits into a 5.25" drive bay (The spot where you could add a DVD or BluRay drive). These are made by HIS, ThermalTake and I think Ultra makes one too. Basically it's a second power supply it can be used to power hard drives, fans or video cards (depending on the model). I used to have one. I worked great.