I have and older laptop and it seemed to start slowing down and lagging a bit. I started upgrading the things I know how to do. First new battery and power supply...no problem. then 1G RAM DDR-667, PC2-5300, SODIMM...no problem. Upgraded to Windows7 Home...no problem. Last, added 1 G more RAM...problem black screen. I powered the laptop down, removed the battery, held power button for a second with no battery and installed the 2nd memory card like I had 1 week prior, but when i put the battery back in and powered it on...nothing but lights (power, internet connection, etc) just a black screen. so I started over and took it back apart and checked it all again. NOTHING. started all over and removed the new Ram cards and replaced with the old 512 cards. NOTHING. a computer guy told me it was the wireless card () But I got a new one anyway and installed it. NOTHING. I am lost and now have $170 in upgrades and O/S and I don't want to throw it away or SELL it for parts. PLEASE HELP. I read your forum first and tried everything you told others to try ALREADY. (no RAM beeps, yes) I know, you're probably thinking $170...why not buy a new one, but I am partial to this one   
I was running Windows7 Home, Microsoft Security Essentials, 80GHD, and basic ADOBE products, GOOGLE Chrome.....Wat U̶̲̥̅̊ need to do un screw d laptop and check d batery connector on d board read it with U̶̲̥̅̊я̩̥̊ meter and clean d ram port den cover it up and check again I did that. it still doesn't work. motherboard or CMOS battery? anyone get a fix with either of these?I'm assuming it doesn't work even with an external screen, thus riling out the screen just not working as opposed to the laptop not passing POST?  And, have you tried removing the CMOS battery for a few hours, or replacing it with a new one?
If so, remove everything you can from the laptop - unplug the keyboard, use one module of RAM, remove the battery, even try reseating the CPU, and so forth.  If it doesn't work in as bare a configuration as is possible, you're almost CERTAINLY looking at a dead motherboard.Is it the correct RAM ? ?