i bought this game from gog, and i got the installer(version 3.0.52.0) and it says its completed, but when i try activating the game installer, its not there, the files empty.

You should try to redownload it again .

i've tried 4 times now

via GOG downloader, avast antivirus

What browser do you use ?

firefox

Install and use these : http://www.flashget.com/index_en.html
http://flashgot.net/

Actually, this has nothing to do with your browser or downloader. RCT1's installer seems to be inaccessible right now, as I figured out while answering someone else with the exact same problem. GOG's link to the setup file is messed up. The only one who can fix this is GOG staff.

Runs fine for me, I didn't use downloader.

I just simply use IE 9. Works like a charm. Maybe you should contact support.

Doest it happen only with RCT?

Try to download one of the free games and tell us if they work or not. You may also want to try downloading RCT on another computer.

If only RCT doesn't work, you should consider contacting support.

i've been able to download 2 ultima's and Caesar 3 and they all work just fine, just cant get RCT1 working

Just an extra confirmation that it works here, I just downloaded (with GOG Downloader), installed and ran it, no problems. So at least it is not a worldwide problem, if the problem is at GOG's end that is.

I noticed though that the RCT1 extras downloaded considerably slower (around 200-300 kbytes/s) than the main installer (near 3 Mbytes/s), maybe they come from different GOG servers.

All bonus content I've been downloading lately reached maximum downloadspeeds of 300 kpbs, whereas most games achieve speeds of up to 3 mbps, so I'm positive that it's not in any way related to the problem.