I've flashed my BIOS on an ASUS P5N-E before, which is very similar to the P5N-D and my OS was W7 64bit. So hopefully I can help.
Here are the steps I took to flash my BIOS using the board's EZ flash utility within the BIOS:
1. First download the latest BIOS file (1204.BIN) and unzip it to "My Documents" for example. Do not rename the file by the way. Just leave it as is.
2. Then format your USB drive using the FAT32 file system. Should be default anyway but check to make sure. Pay attention to the letter assigned to the USB drive. For example, C: for the OS, A: for the floppy, and another letter for your USB drive. Mine for example was assigned J:
3. Then place the 1204.BIN file in the USB drive.
4. With the USB drive still plugged in, restart your computer and get into the BIOS.
5. Navigate to the Tools section and select EZ-Flash 2.
6. When you're in the EZ-Flash 2 window, select the USB drive (remember when I told you to pay attention to the letter assigned to the USB drive? Look for that.) And the 1204.BIN file should show up. Select it, press enter and the EZ Flash utility should take it from there.
Should take a couple minutes (you'll see the progress bar go up and down a few times, it's normal), and as always, never restart or turn off the computer while it's going through it's updating process. It should actually restart the computer itself when the utility has finished flashing/updating the BIOS.
If you have any questions on any of the steps, please feel free to ask.
Originally Posted by roweder
I couldn't get it to do squat, I had all of the hard drives un plugged, so that only the flash drive would be available
I don't think that's necessary. I didn't have to do that when flashing my BIOS.
I just noticed that joelm posted almost the same instructions regarding the EZ Flash utility. I guess I kinda simplified it. But this is what worked for me.