Slow, hot, and loud fan noise problem

I'm on my other laptop and there seems to be some problems. I started it up and it took pretty long time like an old computer. It even takes long time to open programs. It also is hot for a while and then even hotter. When the computer get hot, the fan noises becomes louder. Once the noises becomes loud, it becomes slower. I don't know why, but I need help. It's very annoying. I don't know if it has to do with viruses or malwares. It might has something to do with the computer fans.