yea uninstall sql then delete the whole of the server files folder .
download the server files again from here
http://www.lomcn.co.uk/forum/showthread.php?t=53383 , extract them to c:\ .
Have a good look at the 2 readmes inside the files 1 in main folder and 1 in dbserverfolder.
Then reinstall sql 2000 for XP or 2005 for vista making sure you set it up correctly by using the guide on this post (read it)
http://www.lomcn.co.uk/forum/showthread.php?t=53510&highlight=guide+sql
when youve done all that check dbsrc and !setup.txt for your database name and password that you used when installing sql .
check all the inis and text files as necessary for all the server names and make sure they are all the same.
and make sure that if your running sql serverfiles and client from the same pc that you are not lagging at the select char screen.
EDIT:- leave the files as they are until you can get ingame , they are set up for instant access using lom2 as the db and diamond as the server name tbh you seem to be the only person left having trouble with the black screen. if you do a search for black screen theres loads of info in the posts that come up. (
http://www.lomcn.co.uk/forum/search.php?searchid=275034 )
AS i said do not touch the files until you can get ingame