Do laptops stop working due to massive overheat?

I’ve got a nice dell inspiron I bought about a year and a half ago. But I’m not sure whats wrong with it anymore.. It just freezes up. I’m not sure if its overheated (so many times that the computer is fried?) or if my battery is dead ( my computer won’t hold a battery charge. It only comes on when the charger is plugged in )—- or do I have some terrible virus?

Its obvious that I’m not good with computers. But I’m at a total loss. I do most of my work from home online, and I’ve been spoiled by my laptop – my desktop isn’t cutting it anymore. And I’d hate to buy a new laptop if theres something simple that I’m missing. :(

Any help will be extremely appreciated. I’ll stay online and lurk the thread in case I need to reply to some questions, etc.
I really think it might be a big virus. I have windows vista, and I’ve got that little gauge that tells CPU usage, and even when I just turn the thing on, its all the way to 100% Also, it won’t let me connect to any wifi