Thanks all

.
As it turned out my problem was the simplest of things, (isn't it always so),
I was reminded after reading EROSINSKI's posting that I should CHECK what I might have Inadvertantly STUFFED UP.
Yea!!! I checked what I'd done and NOT done when I'd removed & replaced the RAM as the pc had been seeing only one stick.
I had taken out the power lead to the HHD & DVD as it was interfereing with proper access to the RAM......then removed & replaced the RAM .......BUT left the power lead off.
On rebooting the BIOS msg "on hanging" when detecting HDDs in LARGE RED LETTERS indicated that the CPU speed setting did not match the actual CPU RAM and hardware. Since I had also been playing with tweaking up the CPU a bit at the same time as I'd refitted the RAM I WRONGLY blamed that NOT the simple Bloody obvious STUFF_UP.
So short story...... Check your work, it's very often the stuffup SIMPLE !!!!!