I'm having the same problem! I've messaged Support and they just tell me to use the Downloader, but it doesn't download, The game does have sevre compability issues, as I've tried using Virtual Machines with different operating systems and also using Emulators and graphic changers, nothing seems to work, just errors after erros. The game is Compatiable with my OS but it seems to me that GOG haven't bothered updating their systems, It's been like this for awhile. I prefered when i could just download straight from the site, no problems but now it's all changed, The game is avaliable on steam, incoming forces comes with the orginal incoming, but haven't brought it yet from there as I feel cheated by the company and still trying to figure ways onto downloading this friggen game, so you're not the only one.
Yes, same, I left it alone for years, but been on a compatibility spree, and making all my old games work.
In Steam, a gentleman made an awesome guide on making it work, and I want to see if I can do it. I still have my Incoming CD's. but the whole point was to have everything in Digital.
Here's the guide, and hang on with me, we'll get to the bottom of this! Glad to see not alone. http://steamcommunity.com/sharedfiles/filedetails/?id=809292289