Compaq Deskpro 2000 5200 Problems - No Boot

Although I generally hate Compaqs, I offered to find out what was wrong with a colleague's Compaq DeskPro 2000 Model 5200.  It was an ex-company one and, although it supposedly had worked briefly after the guy acquired it from his mother,  he reported that it wasn't displaying anything at boot and thought maybe it was his monitor.  He had taken it to the local baboon who runs a PC spares place, but he had suggested a new motherboard on the basis that "the hard drive was too large for Windows 95, and Windows XP wouldn't work with the present motherboard" !!!!???

Here's what I did to verify his masterly deduction:

ZIF Socket 7 Pentium 200 CPU, set with the DIP switch to run at 200MHz on a 66MHz bus
Western Digital Caviar HDD Model WDAC21600-60H  (1.6 GB) on Primary IDE socket using single A-B ribbon cable with no slave connector
Original Motherboard Assy. No. 005505-14 Rev BP with Backplane Board (Expansion Board) containing a 3Com 10/100 NIC
2 x 16MB 72 pin tin plate contact EDO SIMM's (matching tin-plate sockets)
256KB socketed secondary CPU cache memory card? (SMART SM364TCSC83XG15)
No added graphics card - using Cirrus Logic on-board chip CL-GD5436-I-QC-C  (not using the video memory upgrade pin connector for additional 1MB video memory)

Here's what I did and discovered:

1. Connected to Standard monitor and attempted to boot, but showed 1782 Disk Controller Failure with 2 beeps
2. This prompted me with alternatives to to boot to Windows using F1 or go to setup with F10
3. Selected F1 but still unable to boot
4. Selected F10 at next unsuccessful boot and found Compaq Utilities recognised the CPU correctly, Showed Primary master as 1,623 MB, Energy Saver On, Video VGA mode, Ser Port 1 3F8 IRQ4, Parallel Port 0378 IRQ7, No CMOS Password Set, BIOS ROM NOT flashable or socketed.
5. Ran Checkup Test which: ID'd Graphics Chip (mode set 640x480 using 1MB memory),  Gave the ROM BIOS revision as 586C, Gave Hard Drive Ser. No. WD-WM3364394179 and Firmware Rev 24-09P08, 786 Cyl, 64 Heads, 63 Sectors per track, Intellisafe HDD Status OK.
6. Saved Checkup Test to Diagnostics Report on floppy (so I know floppy WAS working for write actions)
7. I powered off and swapped HDD jumper to Cable Select (CS) and booted. General Protection Error msodisup.vxd referenced by system.ini.  Operating System Windows 95. Powered off and removed 3Com NIC
8. Booted to DOS and edited MSDOS.SYS to allow boot menu
9. Edited (REM's) lines from system.ini, autoexec.bat, etc all referring to Network logons, to NIC card, and to server-based applications.
10. Successfully booted to Windows95B (4.00.1111.B)
11. Disk shown to be formatted as FAT16
12. Booted once more and did a full RegEdit export, and backed up system files with the intention of uninstalling some of the corporate programmes on it, but didn't get to that
13. Booted PC twice more successfully while considering if it would handle Windows 98, but it failed to boot intermittently on several more occasions and then came back OK another few times without problem again.
14. No ribbon cable on 44x CD Rom, so attached one and tried to test CD.  No response, no LED, changing jumpers didn't help in recognising it
15. Booted to CMOS setup (F10) and tried several ways to get CD Rom recognised, but none worked
16. Linked drive to my own Windows 98 machine as Primary Slave and XCOPIED all the folders over into a folder on my own hard drive as a backup
17. Replaced drive in Compaq and it still booted OK several times more, but did have the occasional blank screen glitch with no monitor signal
18. Didn't run Scandisk because I had a feeling it may affect the Compaq non-DOS partition containing the CMOS data (Compaq Diagnostics report stated BIOS chip did not store diagnostics utilities)
19. PC failed to boot one of the times and, although HDD initially spun up, it spun down seconds later and the LED died with it
20. Found that I was unable to boot to floppy and no LED showing on Floppy Drive
21. CD Rom still not working, and no amount of cable-swapping and jumper-swapping allows the system to boot from floppy, CD Rom or HDD.  Can't boot to F10 CMOS to check boot sequence
22. Currently all the HDD does is spin up for 5 seconds and then wind down snuffing out the LED with it.  No other activity after that and no signal going to monitor.

I have downloaded Compaq Diagnostics and created a bootable floppy from it, but can't boot to it. This would allow me to update the Compaq Partition Disgnostics data files.
I have the correct Cirrus Logic graphics drivers on disk ready for install.
I also have the RompaQ's shown below.

I don't have any other Compaq PC of that age, or access to one, which would have allowed me to implant the HDD, boot to the Compaq floppy, and attempt to recreate or repair the F10 partition data.

I am hesitant to do anything else with the HDD, even though I am perfectly at liberty to format it if I want.

I was sure that the CMOS WAS set to boot from floppy, but I didn't look carefully enough to recall where it fell in the boot order.

I have no way of testing whether the CPU is OK, but I have found that sombody has removed the silicon-based heatsink paste from the CPU/Heatsink interface.

I have no way of knowing whether the BIOS chip is burned out or functional.  I observed all antistatic precautions throughout.

So, my suspicion is that the CPU is not being able to find enough CMOS data on the HDD non-dos Compaq partition due to physical disk damage or corruption, but can't restore this from the floppy.  I have tested another good floppy disk drive on the Compaq, and it still fails to detect the device or disk in it.  Have also tested another CD Rom Drive with the same negative result.

The other possibility is that the CPU has overheated and become damaged due to the absence of thermal compound.  There is a possibility that this has been removed when the technician looked at it and couldn't fix it.  Although the fan was working OK when I was able to get it booted, this may have been the first time it has actually run in Windows since the compound was removed, and has generated too much heat.

I'm about to hand it back to my colleague and suggest either of these 2 conclusions unless somebody has a stroke of genius and can suggest a way to resolve this.

RompaQ's available for use:

1) sp16085.exe version 10.40 A Personal Computer Diagnostics

2) SP12906.exe version 10.39 A Personal Computer Diagnostics

3) SP4711.exe  version  1.23 A F10 Setup and Personal Computer Diagnostics
(Creates two diskettes:
  (a) Computer Setup/V Version 1.23 Rev. A.
  (b) Personal Computer Diagnostics Version 10.19 Rev. C).

4) SP15800.exe upgrades the ROM firmware of a Deskpro 2000 computer with 586C ROM BIOS version to recognize hard drives larger than 8 GB (While not applicable, it's interesting to note that this upgrades the BIOS to 586C_0601.99, whereas the current BIOS is showing 01/05/98 - Anyway, the diagnostics told me the BIOS wasn't flashable !!)

6) SP15413.exe version 3.0 Utility to Reprogram an Electronic Serial Number into BIOS (can occur when the system board is swapped) - Again, Compaq Diag says BIOS isn't flashable

7) SP10200.exe version 1.00 A non-destructive Firmware Update for Western Digital IDE Hard Drives to fix a SMART threshold issue. It corrects false 1720 errors displayed when the computer is started.

8) SP3889.exe version 2.00 A Deskpro IDE PD-CD Support for Windows 95 Windows 95 driver for
an IDE PD-CD drive installed in a Deskpro (Sure Win98 has this support as standard)