RAm Upgrade question

[XabbaRus]

OK my 2 sticks of 1GB 400Mhz RAM came today.
It is 1 GB High Density 400Mhz RAM, my Mobo supports this type of RAM

It is Legacy Industries RAM

I also bough it off of ebay. Now berfor you body slam me for that I am feeling stupid already.
The guy said 100% new answered my questions as to what type and it arrived very quickly.

Now I took out my old RAM which turns out to be 400Mhz RAM too so I could have put the new stuff in along side.

Anyway I put in the new ram, PC boots sees there is 2048MB of RAM during the POST screen and then proceeds, except it gets as far as a black screen.

OK not the GFX card as I put back my original RAM and here it is working fine.
Now the RAM looks new but before I give any feedback maybe I am installing it wrong. I doubt it since I was able to put back my old RAM and the PC is working.

Help a chump out and go easy on him, the wife is already giving me a hard time.