Speaking to a new customer over the phone, it seemed like during POST, the PC failed to detect the HDD, so we suspect a possible HDD fault. 

Once I got there, I could see that the PC would start, get partway through the POST, then freeze.

I started removing components to isolate the problem: removed all drives, an internal modem, yet problem persisted.

Removing the RAM was inconclusive: fans would spin, but there was no POST (monitor stays black, but it could be expected behavior), however, there was no MoBo beep to say “wheres the RAM“? This is unusual (unless the MoBo speaker wasn’t working…

I plug the RAM back in, but now I’m still getting no POST… blast, I’ve just made things worse!

At this point: I suspect its either the CPU, the motherboard, or the PSU.

I tried a new PSU, but the problem remains.

So I put the old PSU back, and I get a burnt plastic smell (I very quickly power off!!!). I look, but cannot see what got burnt.

I’d say that given I could see the POST message (at the start of this adventure), then the CPU must be OK, so the only thing left is the MoBo.

Customer is happy to purchase a new (nearly identical MoBo).

I revisit to re-install, and in the process I find the source of the burnt plastic smell: the RAM socket… looking at the RAM, I see one of the gold connectors is black (possibly charred plastic; or maybe the RAM got fried due to the high current)… things are not looking good at this stage.

Anyway, i plug in the MoBo, connect the CPU, the power connector, and power to the MoBo.

I hit the power switch, and fans start to spin, but the screen stays black, and no beeps 🙁

As a last resort, I decide to try the RAM (which might make things worse)… and I get POST!

I plugin all the rest, and windows actually boots!

XP asks to be revalidated, and I let it do so over the internet.

I update the incorrect video and sound drivers, then my job is done… I’m amazed at how well XP coped with a totally new (but similar) MoBo.

Update:

A few days later, the customer calls with a strange problem with her video display: she says that the text appears very small within each window, and she cannot get the display to 256-bit colour.

I insist that 32-bit colour should be fine (I don’t mention that there is no such thing as 256-bit colour… the human eye is not that good!), as it should also be able to display 256 colour games… I assume she got 256 colour and 256 bit colour confused.

However I cannot picture the problem with the small text… I get her to change the windows font sizes, the IE font sizes, the screen resolution… but its never quite right. She says she will call me out again to fix the problem (once she can afford to).