yes, even if the game is already installed, you still need the disk to run the game.
If you downloaded it from the internet, then no. If you installed it from a disc, you will still need to insert the disc every time you want to play the game.
No, you do not need to be on the game you bought with Gmod to play it although you do need to have the game installed to run gmod and i also recommend having the game Half-Life 2 installed to get most of the textures and weapons and npcs and props that go along with it.
If you have a Mac, You can install all the expansion packs and only need the last CD that you installed to run the game.
Yes you can still play games online after they have been installed on the hard drive.
Nowhere, you need to have the game installed on your computer and the disk to play it.
No you can play games that have been downloaded, but the games from disc never are downloaded when they are installed and you need the Blu-Ray Game Disc (not a CD) to play them every time.
no, if you want to install the sims 2 you do not need the sims 1 installed.
Yes, as long as you can access the account and if the pc has the specs to play the game
Well if you have it installed then just try to open it and if you cant then you would have to buy the disk
You need to have a capture card installed in your computer or have recording software such as Fraps.
it comes with two disks. you need to have both of them to install the game, and after the game is installed you only need disk 1 to play