Since adding a RAID card into my HP MicroServer (N40L) I've been struggling with the loss of my dual port NIC. After looking through a fair few posts where other people have trimmed their card to fit the slot and reading through the PCI Express standard I decided to do it as well.
There are other options, such as cutting the slots on the motherboard and covering the excess pins on the card with tape, however I didn't want to risk any damage to the motherboard.
- Mark the cuts
We want to leave 7 pins, this leaves 2 lanes for the PCIe 1x slot. Version 2 of the PCI Express spec gives us 500MB/s per lane. I'll leave you to do your own math there as my intentions are for segregation rather than speed.

- Mark the back as well

- Sand and file back
I sanded with a Dremel to the point below, then used a file to carefully reduce the remaining bit that looks as if it would hold the card out of the slot slightly. Sanding took about 2 minutes and produced a very clean result. This would be a great time for your phone to not be in your pocket.

- Clean any dust and debris off the card carefully.
- Insert the card and see if it appears, mine shows in ESXi 5.1 as below
