Thinkpad sudden death

purchased a Thinkpad T 21 off Ebay three months ago. The machine had a week's warranty at the time I purchased it. Its 20 GB hard disk was replace with a 10 GB one but the rest was all the same and it worked fine. The only software I put on it was part of the office 2000 suite, kodak easy share, Endnote and Norton antivirus. After I put in all the windows security fixes a couple of months ago, it seemed somewhat slower but it was still working all right.
A few weeks ago, once it behaved somewhat oddly... when I switched it on, it wouldnt immediately light up, but if I turned it off and on a couple of times it would work normally. Last week it started happening again and progressively it was taking longer and longer to light up.(I mean the system would start up but the screen took much longer and sometimes repeated turning on and off before the screen lighted up.)
I remember seeing a flash too once saying that the system was dangerously low on resources. But it didnt show up again when I switched it on the next time.
Last night, when the laptop started but the screen did not turn on I switched it off and tried to turn it on again and my heart sank: the laptop would simply not start up this time. No light, no sound.
I know that the battery was never holding a full charge but I always use it on A/C. I also know that I may have driven it somewhat hard by using it for long hours for writing. But could it be dead ?
Is this some issue with the battery ? With BIOS ? With the mother board ? Electrical system ? Can it be repaired ? Salvaged ?
I will appreciate any tips because, I was banking on this investment to last me through my dissertation... that is at least the next 2 and half years. HELP!