This could be one of two problems, stemming from either your hard drive or your RAM. If your Gateway MA6 is unreasonably slow both during boot up and in the operating system, even with only one program running, it is likely that your hard drive needs to be replaced. If it is slow during boot up, and with many programs running, it would make more sense that your RAM will need to be replaced or upgraded.
Your battery most likely needs to be replaced. This can be easily tested if you know someone else with a similar model computer, by swapping out batteries and testing. The battery on the Gateway MA6 is easily accessible, and there are guides available here. that outline the procedure.
You're cooling fan assembly is mostly likely either clogged, or faulty, which is limiting your computers ability to dissipate heat and run at a reasonable and stable temperature. Replacing or cleaning out the cooling fan will help. You can reference the Cooling Fan Assembly Replacement Guide here for instruction.