Having Problems with my Toshiba Satellite

Operating System: Windows XP (Service Pack 3)
System Model: Satellite M45
Processor: Intel Pentium M Processor 1.73 GHz
Memory: 504 MB RAM

Description of the Problem:

After about three years of having zero problems with my laptop, last week I attempted to use the Internet and my computer was acting funny (which is somewhat normal, as its getting a little older and I run many programs at the same time). So I decided to reboot. However, the computer basically froze at "Windows is Shutting Down" and I had to manually shut the power off (by holding down the button). When I turned the computer back on, the initial Toshiba screen appeared, but it was off-center. It did not go past this screen (normally it goes right to the password I have on my BIOS).

So I restarted again, and again, and the same problem occurred each time. So I let the computer cool down for a while, thinking it might be overheating (as it was quite hot outside that day). I eventually booted it up, and it worked fine. Everything was working much faster than before I restarted it. I figured it was just the heat and decided to keep a fan blowing on it (from a distance) to just keep the air circulating.

Skip to this morning, when we had a thunderstorm. I left my computer on last night and when I woke up, I decided to shut it down and unplug it. So I did that, and once again it got frozen on the "Windows is Shutting Down" screen. I shut the computer off manually. This morning when I woke up, I turned the computer on, then the power immediately went off. I tried again, and the same thing happened. Then I unplugged the power from it and tried, and this time it worked.

This afternoon I decided to see if the computer would do the same thing if I shut it down (which is risky now, since I'm worried the computer won't start up). I shut windows down again, this time it didn't get stuck on the shut down screen and the computer went off, but when I rebooted, it got stuck on the same off-centered Toshiba screen I was talking about the first time. In this case there was no way it was the heat because my laptop was cool. I tried several times more and the same thing happened. Then I unplugged the power and tried it, and it went straight to my password screen. Now, I think the whole unplugging thing is likely just a coincidence, but I just figured I'd mention it because there is a small possibility it could actually have something to do with it.

Does anyone have any insight into what this could be? Oh, and I also just recently upgraded to Windows XP Service Pack 3, but once again I'm thinking it is probably just a coincidence.