Back in the day, my dad wouldn't let me upgrade the RAM and video card in our first PC, until I'd proved myself by fixing something less valuable. I fixed a calculator which didn't display properly, because the LCD screen was loose. I cut a shim out of kitchen sponge and wedged it behind the display to maintain the pressure on the screen. It worked, so I was then allowed into the PC.
I upgraded it from 16MB RAM to 80MB, installed a Voodoo Graphics video card so we had proper 3D acceleration, and overclocked the Pentium chip from 120MHz to 133MHz. Then I played GLQuake, and it was awesome.
I fixed our PVR a while back. I'd attempted to sell it, but the postman dropped something on it so it didn't work. They sent it back to me and I claimed from them and refunded the buyer. I replaced the hard disk and bent the casing back into shape, and it worked fine for another year until I sold it. So, the Royal Mail paid me to keep my PVR. Excellent.