sodapopsmash

Hi, I'm new here and need some help with a laptop I'm having trouble with. So here's the story:
I bought a dell 1150 (2.4ghz, 512ram, 40G HD, xp home) and the owner informed me that it would start up fine and run properly sitting perfectly still, but if it was bumped or moved it'd shut down. I bought it anyways because it sounded like a bad connection/bad solder. I got it home and tried to power it up and the fan would kick on for a second and the power/hd/battery lights on the front would light up, then shut off immediately. I'd remove the battery and try again and it'd just keep doing it. So i researched and found that on the panel on the bottom labeled "c" there are two tabs that over time will press down on a chip, if i remember right its L14VCA or something similar, and create fractures in the solder points. So i tore it down to the bare motherboard, then a friend and i resoldered the 14 points on the chip, reassembled it and it worked perfectly for an entire day and night. I shut it down and closed it, the next morning woke up and it wouldn't power on. SOOO FRUSTRATING. After that i went through a ton of small steps to try to find the problem, but nothing consistent ever happened. Sometimes removing the plastic panel over the screen hinges would allow it to power on, sometimes it'd power on with no screws holding the base together, then when i put screws in it wouldn't power on, removal of cd drive would sometimes let it power on, etc, etc, etc. So i tore it down about 5 more times and still couldn't find anything. Now it will start up find and run for awhile, then crash. Never any bluescreens or anything...it'll be running fine then something will click and the screen will go black and the fan will stop for a second then start again and nothing will ever come back on the screen, the lights on the base are still on and the computer itself is still technically running. The only thing i can do to get a response is removed the battery, put it back in and try again. Does the same running on wall charger. The time is never consistent, sometimes it'll run for 5 minutes, sometimes 15, sometimes even 45-60 minutes before doing this. i cleaned lots of solder points with alcohol and cleared any dust/debris that was near anything important and found that the motherboard battery had a small break in a solder point, so i resoldered the battery and put it back together, but that didn't change anything. I am stumped, and so so frustrated with this thing, I've researched a lot and couldn't find any threads of any forums that really relate to mine. (besides the early problem with the c panel and fractured solder points which i believe is fixed) any suggestions or insight would be greatly appreciated. Sorry for the long post, but i think describing everything thoroughly makes the problem easier to diagnose.
thanks again.
-jim