Remember back in the early 80's when Space Invaders and Galaxians were in the video arcades ? Well here is a damn fine emulator so you can relive the times when you fed all your 10p's into the machines...

I've recently found a better (well easier) version with a windows front end. This is mame32 v035, for win32 (windows 95 interface)
This is easier to set up and run, being GUI based...
Unzip the file ensuring you extract the folder paths. Then simply put the rom zip files into the roms directory. Try this Rom Library
Use refresh (F5) if mame doesn't see the new roms...

DOS Version
Download the files, and unzip the emulator into a directory (example mame). Ensure you extract the files including the folder information.

Create a directory for each game in the Roms directory, the same name as the zip file is a good idea, and unzip the files for that game into it (see screen grab).

Open a DOS window, navigate to the mame directory. To run a game type:
mame galaga
if galaga is the game you wish to run.

Left and right cursor keys to move left/right, 3 to clock up credits, 1 to start, CTRL to fire.
(Those are what I found anyway)

Some of the roms I have

Other games can be found by a quick search using keywords such as mame galaga galaxians.
Also, try this link