None of that hardware or software is supported anymore.  What exactly are you looking for? You can in fact get these systems with windows 10 pre installed.

https://www.walmart.com/ip/55080037

BIOS should be done via DOS or XP.

A22 is recommended for newer OS.

Description	Supported OS	Download
Dell Optiplex 755 System BIOS A22 This package provides the BIOS Update for Dell OptiPlex 755 running the following Operating Systems: Windows and DOS.More details	BIOS
DELL,DSK PROG,BIOS,OPTI-755,,A21 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A19 This package provides the BIOS update for Dell Optiplex 755 running the following Operating Systems: Windows and DOS.More details	BIOS
Dell OptiPlex 755 System BIOS, A17 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A16 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A15 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A14 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A13 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A12 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A11 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A10 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A09 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A08 OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A04 Dell OptiPlex 755 System BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A03 Optiplex 755 BIOSMore details	BIOS
Dell OptiPlex 755 System BIOS, A01 Initial BIOS release.More details	BIOS

The 755 supports XP, VISTA.   Windows 7 8  10 work on this model but they are not supported.  Dotnet and Directx June 2010 will need to be re applied for xp, vista, 7 ,8 , 10

This isn't a big deal as most of the drivers are native to windows.  You only need to add the audio chipset and INTEL RST 10.1.0.1008 drivers and the INTEL AMT HECI SOL Drivers for windows 7.

http://downloads.dell.com/published/pages/optiplex-755.html

Description	Supported OS	Download
Intel AMT SOL/ LMS, v.3.2.20.1049 PV, A02 This package provides Driver for Intel AMT SOL/ LMS and is supported on OptiPlex 755 running the following windows operating systems: Windows 7, XP, Vista.More details	Windows Vista 32-bit Windows 7 32-bit Windows 7 64-bit Windows XP Windows Vista 64-bit Windows XP x64
Intel AMT HECI, v.3.2.20.1049 PV, A02 This package provides Driver for Intel AMT HECI Chipset and is supported on OptiPlex 755 running the following windows operating systems: Windows 7, XP, Vista.More details	Windows 7 32-bit Windows Vista 64-bit Windows XP Windows 7 64-bit Windows Vista 32-bit Windows XP x64
Intel Chipset Driver This package provides the driver for the Intel Chipset and is supported on OptiPlex, XPS Desktop, Precision, Latitude and Dimension models that are running the following Windows Operating Systems: XP and VISTA.More details	Windows Vista 64-bit Windows Vista 32-bit Windows XP Windows XP x64

Description	Supported OS	Download
TEAC CA-400 Enhanced 19-1 Card Reader Driver This package provides the TEAC CA-400 Enhanced 19-1 Card Reader Driver and is supported on Optiplex 740/755/760/780/960/980, Vostro Desktop 220/420/220s and Precision T3400 that are running the following Windows Operating Systems: XP (32/64-bit), Vista (32/64-bit) and Windows 7 (32/64-bit).More details	Windows XP Windows Vista 64-bit Windows Vista 32-bit Windows 7 32-bit Windows XP x64 Windows 7 64-bit

Description	Supported OS	Download
Analog Devices ADI 198x Integrated HD Audio, v.6.10.x.5491, A02 Analog Devices HD Audio driverMore details	Windows Vista 64-bit Windows Vista 32-bit

Wow, Thank you for the links. I am looking for two things:

1. Graphics Card

the graphics card update. The system shipped with a radeon card, but according to win 7 x64 device manager, the graphics card is "Intel Q35 Chipset." So, I am trying to confirm the manufacturer of the physical card, not the chipset embedded on the card.

2. Unknown PCI Card (serial)

Something is installed on my pc that is not recognized by windows. Uninstalling it fails as it reloads each reboot. Any ideas on hot ro determine what is attached to the PCI slot that uses the serial port???

So, rather than bother with Dell's system configuration app (which apparently fails to work if your system is out of warranty - a really lame and aggressive tactic that embitters dell customers like me) I used Belarc to look into the box.

Finally, walmart could sell an OptiPlex for $150 and probably wouldn't buy one, or at the very least, I'd wipe the HD and install a less intrusive OS.  Once Win 7 goes the way of XP, I will move to a Linux based OS.  I would rather use a 1970s era calculator or a Dell 486 running Win 3.1 then  install Windows 10 on any of my pcs. I used W10 for about 3 weeks and that experience was enough for me.

Thanks again!

Assuming the PC boots, you can always look in Windows Device Manager to see all the currently installed hardware and/or run msinfo32 from Start>Run.

"Unknown PCI Card (serial)" is chipset and AMT HECI SOL drivers.

All Radeon HD series cards from 1000 2000 3000 4000 5000 6000 7000 8000 series are legacy.

http://support.amd.com/en-us/kb-articles/Pages/Software-Support-Legacy-Graphics.aspx

These systems shipped with Radeon 2400, 2600, 3450 cards.  Which all series before 5000 and up use the earlier legacy driver.

Users with AMD Radeon HD 4000 Series and older products looking for driver support, please refer to KB article:  Driver Support for AMD Radeon™ HD 4000, HD 3000, HD 2000 and Older Series

  If you are looking for an upgrade from there only specific ASUS HD6450 cards fit into the SFF Desktop or Mini Tower.  USFF has no slots and therefore NO card at all works.