Judging by posts here this game is very capricious as regards to system requirments and hardware.

So can I make it run on my quite old rig, Win7*32, 2GHz CPU, 4Gb RAM and 1Gb middle-class NVidia graphic card?

Yes, you should be able to run it. The minimum system requirements:

Windows 7
Intel Core 2 Duo E5200
4 GB RAM
GeForce 9800GTX+ (1GB)

If you are not sure, you can always buy it via Steam and refund it before you've played two hours. I don't know if GOG already has this service. I hope you have fun with the game. It's really, really good! :)