Hi hopefully this is an easy question to answer for you experts...
I'm upgrading a sony desktop. It has 2 PCI cards - tv tuner and ethernet cards. I want to switch them. (tuner card is bigger and next to the pci-express slot). When I put the graphics card in, cables touch the tuner card.
Do I have to uninstall these cards before I switch them?
No you shouldn't have to uninstall\reinstall them at all. As long as we're just talking about both cards being regular old PCI cards, and we're not referring to your PCI-E graphics card swapping anywhere you can.
Just shut down the computer, flick the power switch at the back of thre computer (should be a little 1/0 switch on the PSU next to the power cable), but make sure you leave the machine plugged in physically with the cable. If you flick the switch on the PSU to off and leave it plugged in, the PC will essentially ground itself to help prevent against any possible electric shock you may cause to the system. Then open up the case, touch something metale (ie. the steel case itself) and then go ahead and switch the cards to w/e PCI slot you want to.
That was probably more explanation than you needed, but its always better to be safe than sorry when messing with internal PC components... I've done my fair share of damage to a laptop or two without proper grounding.
You can just switch them, but the OS may see them as different devices because IRQ setting may be linked to each physical slot, if so the hardware will work on reboot, but you may loose settings like IP setup on the network card.