Just downloaded and played a game called PixelShip. Don't know if anyone has heard of it. Kinda playes like defender without saving people from aliens. You fly around shoot other ships, turrets and collect coins. After you have wiped everything out, you face a boss if you defeat him you get his ship. Really neat game done in retro style like an old dos game, but plays fine on xp and requires few resources. Shareware version is keeping me entertained. check it out at
http://www.pixelships.com/pxs_details.html
didn't see a topic for it and I searched. Sorry if this is a repeat though.