I just did this mod. I didn't do any flashing or software update 1st, went straight for the hardware. Basically the first thing I did was use Dell Service Manual to install card as instructed.
I then booted up and the screen looked fine initially, then when it went into windows, it was skewed. (I was at the nvidia 84.25 with laptop2go inf updated for my 6800). Basically it looked like them old TV with the vertical sync setting cranked all the way to the extreme.
So now for the software bullshit. I first downloaded the XPS bios hack (IXPS2A01.Hacked.EXE), copied it to a folder. Since I am at work, my work PC doesn't have a burner or floppy, but it does have the USB. So I went to the bootdisk site mentioned, and all their EXEs want an actual A: or B: drive and my USB was an F: drive in win2k. So I went to manage and tried to redirect the drive letter with no success. I then went to the bootdisk site mentioned at the beginning of the thread and grabbed win98c.zip and winima61.zip (Non-Windows Based Image Files W/ImageApp and win image further down the page). I used winimage to extrace the img file from win68c.zip to a folder and used this folder to feed the hp usb format utility.
I booted on my 9 cell battery with this using F12 to get the USB device, ran the exe, flashed the BIOS. Rebooted and viola, still skewed.
I rebooted again, pressed F8, selected VGA mode, reinstalled the NVIDIA driver and the also the bluetooth (it prompted me???) and viola, I am whole again.
(1) Go straight for the hardware. Install the card as instructed.
(2) Plug a USB key that you can blank out into your other internet connected PC
(3) Download winimage and win98c.zip from bootdisk website (here are links, not sure how long they will be good, http://www.winimage.com/winimage/winima61.zip
(4) download HP utility from this post on first page
(5) extract bootdisk IMG file from win98c to a folder using winima61.zip's included winimage
(6) boot the laptop with this USB, pressing F12 to use usb device as bootable.
(7) flash away
(8) reboot with F8 and use VGA mode
(9) reinstall nvidia drivers