Problem adding memory card

That I recently purchased a memory card of 1 mega to optimize my computer (pentium 4). When I inserted the new card and I restarted my computer asks me to insert the Windows XP CD. Then nothing happens.

I returned to the merchant and he tested my card. It runs on other PC without problem.

Could you help me install this ?

Thank you in advance for your invaluable assistance.

Can you give more information about your hardware, if you like, especially the reference and the name of your motherboard.
Which brand is your memory card?

Here is some information on my computer.

I hope this will be sufficient:

Intel Pentium 4 CPU
2.00 GHz
256 MB ram

Is your PC card that supports 1000 MB of RAM?

You can see here what are the possibilities of extending the RAM for your computer:
http://www.crucial.com/

This could be eg 2X500MB instead of 1x1000MB.