[Trouble Re-installing GTA 4, retail disc, any ideas?]

Hi there, thanks SO much if anyone can help me out. I bought GTA 4 for pc the other day, installed it, had a fun time playing it. I decided to mess around with modding and it messed my game up and stopped it from loading the actual game. I deleted it from my PC, after deciding I'm fine with just re-installing GTA and playing the game clean and unmodified. So after deleting it from my computer, I have tried reinstalling the game via my retail discs..However I can't get past the first set up screen now, after inserting the disc it gives me the option of launching Social Club or Exit. When I click Launch Social Club, nothing happens. I've included a link to the screen I get.

I'd GREATLY appreciate it if anyone could help me. thanks a ton.

http://imageshack.us/photo/my-images/684/unledkd.png/

[Help with gta trilogy mac san andreas mods/multiplayer]

Hello everyone, I recently downloaded the Mac version of san andreas from Gametreemac.com, they have the entire trilogy up. Anyway, I've loved it so far but I don't know how to install mods or the multiplayer component on my mac version. Any help would be GREATLY appreciated. I think it's a cider port?