Thanks.
I will try these possibilities.
However, on an urgent work I will be away fro three weeks from this PC.
And will report the results after that.

Friends,
I am back at the PC.
To see whether overload is the problem, I took away the nvidia card, the extra 2GB RAM.
The PC boots with network up from cold boot.
The overload could be the problem.
However, I need the nvidia card and the extra 2GB RAM.
So, I am booting the system with Ctrl+Alt+Del at the grub screen, and then let it boot up.

This is not a clean solution. But a work-around for speeding up the booting process with network.
Should I mark the thread "Solved"?
Thanks

Hi...

I'm wondering if an PSU upgrade might be the solution here or if there was some issue the motherboard was having with the extra memory module(s)? Some motherboards are very picky.

Regards...

It's not solved.

*if* it's due to a PSU problem, you are living on the bleeding edge.
What size does your PSU claim to be?

PSU looks to be 200W, as DELL specification says.

The hard disk used in this system was 1TB.
But DELL specification says it supports upto 500 GB.
Checked with other similar Optiplex 9010 systems; all of them have 500GB.

So, replaced the hard disk of 500GB capacity.
It works well with nvidia card and 4GB RAM. (Dell says it supports 32GB)
The network is now up with cold boot.

Very Sorry, I did not observe the hard disk capacity.

Wondering why Win 7 was working all right. May be it required Ctrl+Alt+Del to log in; and that was doing the trick?

Hi...

Looks like your problem has been solved. If so, please mark this thread as "SOLVED." Excellent job of sticking it out until you could determine the source of the problem!

Regards...

Hard disks take virtually nothing (perhaps a slight surge on initial spin-up).
Motherboards take a moderate amount.
CPU takes a lot.
Video takes a lot.

I would generally always go for an uprated PSU:-
Both my desktops are 450W - even though the manufacturer says the components only use 280W.