Hey guys, I'm looking at the site and I'd really like to revisit old favourites like Master of Orion II, Settlers II and the original Fallouts.
Problem is, I've tried installing these games off the old original cds/collections before, and in every case it's failed on modern rigs, showing some horrible graphics errors etc., so are the GOG versions somehow augmented to be compatible with modern computers, and if so, is there a solid guarantee that the game I buy will work on my rig?
Thanks guys.
Specifics:
i7 2,80 ghz
8 gigs memory
Geforce GTS 250
Windows 7 Home Premium x64

gog games come with their own installer and often apply patches or workarounds for issues. in same cases they even come with some sort of emulator (DOS or game-specific).
In most cases this works well enough, though there are a few exceptions (like Sanitarium). If you have any doubts you should check the forums of the game you want to buy - you will see if there are widespread problems.

Thanks a lot for the replies guys (and the welcome).
I figured they'd be doing stuff like that, and I can see that a guarantee would be iffy when you're dealing with various rigs and setups and undoubtedly a million human errors, but I just wanted to make sure that they did a lot to ensure that most people could play these games.
I'm gonna roll the dice, the prices aren't exactly gonna ruin you here.

You do that. As a fellow Dane, let me welcome you to the site, and say that I absolutely love this service. I've had issues with only a couple of the 70+ games I have from here, and as you point out, considering what I paid for the lot, I'm more than satisfied.

If you do have problems they also offer support so you could always try asking them for some help.

Yeah, that would've been plan B, but it's my experience that companies like these usually have a lot of support to attend to, so I figured I'd hit the forum first and spare them a silly question.
Anyway, I have bought the MOO pack and MOO 2 works like a charm so far, much unlike my old copy, so that's 100% of my GOG games covered so far! Awesome.
Thanks again for the welcomes guys.

Note Windows 7 isn't officially supported yet but most games work fine, and you can verify usually in each game's thread. Check the stickied thread in general discussion for more info.
Glad you're happy with MOO. :)