Here's something I found doing a Google search for getting PCI-E 3.0 enabled
"For those of you who have been asking the directions on how to enable PCI-E 3.0 within Windows 7, here are the instructions!
These are instructions on how to enable PCI-E 3.0 using the REGEDIT function within the Microsoft Windows 7 operating system:
Hardware requirements in order for these directions to work properly:
1) Motherboard is PCI-E 3.0 hardware certified
2) Graphics card (NVidia or AMD) is PCI-E 3.0 hardware certified (currently, NVidia 600 series cards and AMD 7000 series cards are PCI-E 3.0 hardware certified)
NOTE: I highly recommend you ensure the motherboard is updated to the most current BIOS version and that PCI-E 3.0 (GEN 3) is enabled within the motherboard BIOS settings.
CRITICAL!! Back up your registry before proceeding! This will ensure that you can restore your registry should you enter an invalid value or conduct one of the steps incorrectly.
Step 1: Update your graphics drivers to the latest version (doesn't matter if you use the WHQL or beta version) and restart your computer.
Step 2: Download the latest version of GPU-Z:
Step 3: Run GPU-Z and verify that the “Graphics Bus interface” value shows PCI-E 2.0 for each card
Step 4: Disable SLI -or- Crossfire (if enabled). If SLI -or- Crossfire are not enabled, skip to Step 5
Step 5: Click on the Windows button (located on the lower left corner of the start bar)
Step 6: In the search index entry window, type in “Regedit” (the Registry Editor window will open)
Step 7: Select the following registry:
Step 8: Identify the correct registry folders for each of graphics cards you have installed. There will be one associated folder for each card installed. To identify the correct folder for each card, you will need to review the names of each folder within the “HKEY_LOCAL_MACHINE/SYSTEM/ CurrentControlSet/ Control/Video” registry directory. The folder associated with a graphics card will have three or more subfolders (depending on how many PCI-E slots available on the motherboard). The values listed for each subfolder will be 0000, 0001, 0002, 0003, 0004, and Video. Review only the subfolders labeled as "0000". You will know you have selected the correct "0000" subfolder when you see a registry labeled “DriverDesc” with a value that matches the graphics card you have installed. Example, the value in my “DriverDesc” registry value reads “NVIDIA Geforce GTX 680 - Titan - 780(ti).
Step 9: Right click on the folder labeled “0000”. Select “New”, then select “DWORD (32-bit) Value“, then enter “RMPcieLinkSpeed” for the name of the registry.
Step 10: Right click the “RMPcieLinkSpeed” registry you just created, then select “Modify”, then enter “4” as the data value and verify that the “Hexadecimal” option is checked under “Base”, and then select “OK”.
Step 11: Repeat steps 9 and 10 for each graphics card associated folder (named “0000”)
Step 12: Once you have completed creating the RMPcieLinkSpeed registry for each card, close the Registry Editor window and restart your computer.
Step 13: Once your system is back into Windows 7 operating system environment, run GPU-Z and verify that the “Graphics Bus interface” value shows PCI-E 3.0 for each card.
Step 14: Re-enable SLI -or- Crossfire as needed.
CONGRATULATIONS!! PCI-E 3.0 is now fully enabled within Windows 7
*UPDATE* Please note that if you update your graphics drivers, this registry hack will be undone and PCI-E 2.0 will be enabled again. Due to this issue, I added a step at the very beginning of these instructions to have you update the graphics drivers BEFORE doing the registry hack. Hopefully, this will save you a bit of time and hassle. "