If I bought a graphics card with 1 g memory on board,but have 400 ram in
computer does that mean i'll get 1.4 g of ram wHEN NEW CARD IS INSTALLED?
Yes and no.
Yes, you have 1.4GB of RAM, but that probably isn't what you mean.
Windows will still report 400GB of RAM (but see below) and that's how
much will be available to the operating system and your applications.
The RAM on the video card is used only by the video card, for
displaying images on the screen, and is not otherwise available to you
for the things system RAM is used for.
But presumably you currently have no video card, and instead have
video support on the motherboard. If that's the case, that video
support is using some of your system memory, and when you install the
graphics card, you can give back that memory for use at system RAM.
You probably have 512MB of RAM, and 128MB of that is used for video
support, leaving you with 384MB (not 400MB). Once you install the
video card, you will be able to use all 512MB of your RAM, not just
the 384 you presently can.