On Fri, 6 Jun 2008 02:53:30 -0700 (PDT), peter
<solvino@googlemail.com> wrote:

>A week or so I posted a message about upgrading the memory and the
>replies were very helpful. I bought some memory online and opened up
>my PC. There were two memory slots and one was hard to get at as the
>video card was in the way. So I took out the video card (carefully)
>then popped out the two memory cards. Then I realised that I'd bought
>the wrong memory card!! Silly me, never mind I'd only lost a few
>pounds, so I put the old memory cards back and the video card.
>
>Trouble is that the PC now doesn't work:
>
>1) PC starts up and you hear the drives start to turn
>2) There is nothing displayed on the monitor
>3) The PC gives three long beeps, pause, three long beeps etc etc.

That means that the video card is malfunctioning.
And given your story: you failed to properly reseat the card :-)

--
Kind regards,
Gerard Bok