Dell XPS M1730 laptop problems?

I've had this computer for about 3 years. The first year I got it, it was working fine, it was moving a little slow though. No one really uses it besides me unless they need to so we just keep it in my room . Now its really slow and laggy. It takes 10 minutes for the internet to load. When I first start the computer up, it keeps saying that there is a disc problem of some sort, and it says you can exit this if you press any key in 10 seconds. I always just ignore it. Also, my battery is messed up. I have to keep it plugged it 24/7 if I wana use it. It doesn't charge. When I scroll over the battery icon to see if its charging it says that no battery is detected, but obviously there is a battery in the system. Its starting to get annoying when I try to get on the computer and it takes so long to do everything that I don't even wana use it anymore. Please help, thanks in advance.