Configuring upgraded GX1 for Dual Monitor support on WinXPSP1

I've tried everything I know to get dual monitor support going on my much-upgraded Optiplex GX1. This computer has been nothing short of a workhorse so far in it's lifecycle.

My question is: Short of installing a two PCI display adapters, can I get multiple monitor support from this machine as configured (since I don’t want to give up my 1394 PCI card in the first of my 2 PCI slots)?

AtDhVaAnNkCsE,
David

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Lurid Configuration Details (for potential solution provider or late-night geeks with nothing better to do than read OEM Support Forums):

I’m attempting to install a PNY-packaged  nVidia GeForce4 MX 440 SE PCI (GF4MX440SEPCI). Loading both default WinXP driver and downloading nVidia ForceWare 81.98 drivers. As others have experienced, the onboard Display Adapter (RAGE PRO TURBO AGP 2X 8Mb) is disabled when the PCI video card is installed.

The BIOS I'm using (A07) doesn't seem to have a feature for setting Primary Video Controller. WinXP actually configured the new adapter correctly, but didn’t recognize the onboard AGP adapter. Well, it “knew” it was there – it showed in Device Manager, but with a yellow exclamation noting that the device could not start (code 10 – I believe). Removing the device and reinstalling simply mucked everything up – couldn’t reboot successfully after that except in Safe Mode.

Current Config:
General Information
Service Tag                  5PFP4
Computer Model               OptiPlex GX1 800S+
BIOS Vendor                  Dell Computer Corporation
BIOS Version                 A07
(Older BIOS needed to support CPU Upgrade described below)
BIOS Date                    08-04-99
Windows Version              Microsoft Windows XP Professional
 (Version 5.1 (Build 2600.xpsp2.050301-1526 : Service Pack 1))
(SP2 not supported on BIOS A07)
 
Processor
Manufacturer                 Intel(R) Celeron(TM) CPU                1400MHz
Clock Speed                  1.4GHz
L2 Cache Size                256
 (PowerLeap CPU Upgrade: PL-iP3/T 1.2 GHz / 100 MHz FSB Intel "Tualatin" Celeron)
 
Memory
Page File Size               1406.4Mb
Virtual Memory               1982.0Mb
Memory Slot 1 [DIMM_A]       256Mb
Memory Slot 2 [DIMM_B]       256Mb
Memory Slot 3 [DIMM_C]        64Mb
 (about the only thing left to upgrade here is to fill MemSlot3 w/ a 256Mb DIMM)