I wanted to run 3 monitors on my PC but it only had a single video card slot. That meant I could only run 1 video card and a single video card usually only supports 2 monitors. Some high end cards support 3 or more monitors but of course I wanted to do this on the cheap! I'd heard it was possible to install a second video card by cutting most of the pins off a 16x PCI Express card and installing it in a 1x slot. It sounded like a bit of an internet myth but it turned out to be true and has been running in my PC for many months.
The photo below shows the available slots for my motherboard. The blue one on the left is the 16x PCI Express slot that takes a video card. The next 2 slots are the old style PCI slots. Installing a video card in one of these slots would be possible but I don't have one, they can be hard to come by and tend to be very old cards. The 4th much smaller slot there that is labelled "PCIEX1" is the PCI Express 1x card. This is effectively the same as the blue slot except cut short. A video card won't physically fit in this slot because its pins are much longer. However, it is actually possible to simply cut the extra pins off the card and it will work.
Step 1: Marking the location to cut
The first step is to obtain a PCI Express video card. Decent cards can be obtained from ebay for around $10. Before cutting anything it's a very good idea to mark the pins that should be cut off. We want to cut all the pins off the larger section of the card except for the first 7 pins. In the second pic here I've used a marker to mark the 8th pin. This pin and everything to the right needs to be cut off.
Step 2: Cutting the card
The next step is to actually cut the pins off the card. The best tool for this is a Dremel with the mini angle grinder blade. I guess you could use a full size grinder or maybe a hacksaw but I haven't tried either of those. Note that I have created a notch just near the 7th pin. Without this the card doesn't sit fully down into the motherboard. I have also cut off the lug towards the back of the card for clearance. This may be necessary to clear capacitors and other items that might be attached to the motherboard. After cutting the card use a razor blade, screw driver or kitchen knife to clean up the edges along the cut. I did this to dislodge any pieces of metal that might be hanging around. Then I cleaned off any dust/metal fragments.
Step 3: Install the card
After this is just a matter of installing the card into the computer. You can do this with or without the main video card installed. This is really just like installing a standard video card. The only difference is that you should take extra precaution to make sure the card isn't in contact with anything metal. Remember that there will be very small points along the cut that could be live. If metal is sitting close to where you've cut the card then maybe place some electrical tape along the cut.
Now just hook up a monitor to this card and power on the computer. There is no need to install the other video card and no need to run 3 monitors just yet. If you get anything showing on the screen then it has worked. Now just shut off the computer, install the main video card and you're done.
Step 4: The results
The end result is a computer that will run up to 4 monitors quite nicely. In my case I am running 3 monitors via DVI connections. I don't play games but I believe the 3rd monitor will be slower for games because the bandwidth between the motherboard and the card is reduced to 1/16th of it's original speed. This is still more than fast enough for windows though.