Right click on your desktop and select Personalize.

Then select display settings.

You should see this screen:


From here you should be able to set each displays resolution (laptop and TV) individually, provided it is set to 'Extend the desktop to this monitor'

It sounds like you may have had your displays 'cloned' (each screen shows the same thing and both use the same resolution)

If that doesn't work, your video card should have a control panel icon that has more advanced controls.

If it's just the desktop image - ie no taskbar and you can move an open app from one screen to the next, then it is already in extended mode and therefore 'un-cloned'.

Prior to the trouble, did your taskbar appear on both the laptop screen as well as the TV?

Or was the TV the only screen functioning when plugged in? ie the laptop was disabled while the TV was being used?

It may be worthwhile unplugging the vga, setting the laptops screen back to it's native resolution, reboot and then try re-attaching the TV.