Computer won't boot-black screen only

Hello,

I have an laptop HP Pavilion ze5600 with Windows XP home edition. I received an error message regarding Memory dumping while I was on line answering e-mail. The message did not stay long enough for me to write down error codes but did say if this was the first time this happend to restart the computer which I did. Worked for a couple of minutes and then same message. When tried to restart computer this time, just black screen. No cursor, no message, did not move to any further screen. I know this sounds ridiculous but if the computer sits over night, I am able for one time to hit F8 and get safe mode and other options. First time I was able to get in I went to Last Known Good Configuration and did a system restore but computer froze at tail end, so bad date choice. I did try numerous times to get in again, but could not. Second time I got in I backed up information I needed using Roxio but had to go to work, get kids to school etc so after inserting second CD, I didn't watch what happened and came back to a screen discussing memory dumping and then could not get into my computer. This morning able to get to Last Known Configuration but then computer froze at window showing Window logo, am going to try and get into to Safe Mode tommorrow and try to run virus software. I have tried numerous different things trying to get past black screen. Boot with only ac, Boot only with battery, hold down power button without battery or ac and then use both to boot, tried to boot from XP cd, took out and reinserted RAM cards, tried to start with only one RAM card. Other information is that sometimes fan is running. Hard drive light is always blinking, looks like it is trying to boot from cd because cd light is blinking. Cap lock button will not turn off or on cap light and sometimes that row with cap light buttons comes on and sometimes not. no light for touch pad. Any help would be appreciated. I would say I am a computer novice I have a basic understanding and have kept a Gateway with Windows 98 functioning from which I am typing now. Thank you in advance.