My Maxtor 4 500 GB hard drive sounds like it's trying to run, but then it says that It's not connected to my computer. The little front light is lit up, but then it says it's not connected to my laptop. It's been working great before now?

This could be something as simple as the cable has gone bad. I would replace it first. If that does not work try this.
1.Right click the My Computer icon on desk top. If you do not have My Computer on the desk top it can be found in the Start Menu. It may just say Computer.
2.After right clicking it go to Properties in the drop down menu and left click it. You will get a window looking like this.

If you have Vista. I think Windows 7 is similar. Windows XP will be a window with tabs at top.
3.Open the Device Manager and you will get a window with a list of devices that are installed on you
PC. Looking like this.
In the list you should see your Maxtor it's probably down in the USB section. If you can't find it, it means you need to reinstall the drivers. If you do find it right click on it. You will have a drop down menu with different options on it. You can try uninstalling it reboot the PC and see if it auto finds it.

Hope this was helpful.
Good Luck
cookEmonster