The official site for downloading GTA1 is the Official R* Site. You have to fill out a form (only real info you need to put are age and email address). They will then email you the link to download it.
If your PC seems to freeze when extracting or installing the zip, simply go make a drink, watch some TV and check back every few minutes. It's just a very, very long procedure to unzip 350MB!
NET GAME GOES TOTALLY DIFFERENT FOR EACH PLAYER:
This is a known problem when using different operating systems for multiplayer games. The symptoms are that you will see your opponent running around randomly, with no real aim at all. They will see you doing the same thing - this is due to a synchronization failure, where the players end up playing ghosts. The only way around it is to use the same version of Windows as your opponent.
CAN'T CONNECT TO IP FOR NET GAME:
GTA1 does not work from behind hardware firewalls, routers or some other types of LAN. You can try to bypass the router or hardware firewall and connect your PC directly or open ports on your router. If you really can be bothered, that is.
OPTIMISATIONS (GAME RUNS TOO SLOW)
Q: Is there anything I can do to speed up singleplayer in the Windows GTA1?
A: Click start button > run > dxdiag > sound > change sound acceleration to basic or none. Remember to change it back for other games. Push F8 to turn the frame rate limiter on or off. Push F11 to change resolution.
Feel free to post your own optimisations, any problems you are having and any solutions.
Edited by Sektor, 21 July 2009 - 11:45 AM.