All modern PC components will fail after a while. When a graphics card or RAM stick dies, you can usually keep using your computer until replacement parts arrive, but a failing power supply will bring your entire PC down with it. It doesn't hurt to have a backup PSU, and now you can get one for just $16 after rebate.

The Corsair VS550 is an 80 PLUS power supply, with a total output of 550W. It's not modular, but the cables are sleeved. There's a single 120mm fan on the top of the unit. Nothing special, but it will get the job done.

The PSU is listed for $39.99, and when you enter coupon code EMCPYRU73 at checkout, you get $4 off. On top of that, there is a $20 mail-in rebate that drops the total price to $15.99. You can buy the Corsair VS550 from Newegg.